WESTERN DELTA UNIVERSITY, OGHARA

BACHELOR OF NURSING SCIENCE

LECTURE NOTES PREPARED BY PROF IGHODARO IGBE

INTRODUCTION TO PHARMACOLOGY I
Course Code: PHM 301
Placement: 300 Level, First Semester
Duration: 30 hours lectures
Credit Unit: 2

INTRODUCTION
This course aims to provide a fundamental understanding of the pharmacological use of drugs
that the nurse needs to provide safe and effective care to the Patient. It is vital to comprehend not
only the mechanisms by which drugs impact the human body but also how a client’s
physiological factors influence drug responses.
Safe medication administration is a vital component of the nursing role. Every day, nurses make
critical decisions regarding the safety, appropriateness, and effectiveness of the medications
administered to their clients. To make safe decisions regarding medication administration, the
nurse must have a strong understanding of pharmacology, the science dealing with actions of
drugs on the body. Symptom management and a client’s overall well-being are strongly
connected to the appropriate administration of medications prescribed in a client’s treatment
plan. Before a student nurse reviews a medication order, checks a medication administration
record, or removes a medication from a dispensing machine, it is essential to have a foundational
understanding of how medications interact with the human body

History of Pharmacology
The word pharmacology (from two Greek words, pharmakon, which means “drug” or
“medicine,” and logos, means “study”) essentially means the study of medicine; it could also be
described as the study of the biological effects of chemicals on the body. The history of
pharmacology dates back thousands of years, most likely beginning with the use of medicinal
plants and herbs to relieve symptoms of various diseases. Herbal medications have been used in
medicine in most civilizations around the globe dating back to ancient times.
It is true that although many treatments or remedies were simply ineffective, others unfortunately
were poisonous. However, some treatments did contain substances that worked. Opium, from the
poppy plant, has been used for centuries to relieve pain and for sedation by the Sumerians and

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the Greeks. However, the first authentic use was recorded by the Greek philosopher
Theophrastus in the 3rd century BCE
In the 19th century, pharmacology became a formal science with advances in chemistry and
physiology. Scientists like Rudolf Buchheim established the first pharmacology laboratory in
1847, and his student, Oswald Schmiedeberg, is considered the "Father of Modern
Pharmacology." They emphasized studying drugs' effects on specific organs and tissues.
Scientists in the 1890s developed aspirin from the bark of the willow tree, using it to treat fevers
and mild discomfort. The link between diabetes mellitus and the pancreas was established in
1889 through the work of Joseph von Mering and Oskar Minkowski. Approximately 30 years
later, in 1921, Frederick Banting and Charles Best formulated the first insulin preparation.
Paul Ehrlich introduced the first treatment for syphilis in 1909 by isolating a chemical compound
that could be used against a microorganism (arsphenamine, or compound 606). Arsphenamine is
a derivative of arsenic, and although it could successfully treat syphilis, it did have potentially
fatal side effects, which caused it to fall out of use quickly. Shortly after that, in 1928, Alexander
Fleming discovered that Penicillium notatum mold prevented the growth of Staphylococcus
aureus and ushered in the era of antibiotic use. Millions of lives have been saved since then by
using antibiotics to treat infectious diseases such as pneumonia, sepsis, gangrene, scarlet fever,
syphilis, gonorrhea, meningitis, and tuberculosis.
Today, pharmacology integrates fields like genetics, biotechnology, and nanotechnology,
offering precision medicine and targeted therapies. For nurses, understanding pharmacology is
crucial for safe medication administration, patient education, and recognizing adverse drug
reactions. This historical foundation highlights the progress from traditional remedies to
evidence-based, life-saving therapies.

Importance of Pharmacology in nursing

Pharmacology plays a vital role in nursing practice, ensuring safe and effective medication
administration, patient education, and improved healthcare outcomes. Below are key reasons
why pharmacology is essential in nursing:
1. Safe Medication Administration: Nurses are responsible for administering medications
accurately. Knowledge of drug classifications, mechanisms of action, side effects, and
proper dosages helps prevent medication errors and adverse drug reactions.
2. Patient Education: Nurses educate patients about their medications, including proper
usage, potential side effects, drug interactions, and the importance of adherence to
treatment plans. This empowers patients to manage their health effectively.
3. Understanding Drug Interactions: Nurses must be aware of possible drug-drug, drug-
food, and drug-herb interactions to prevent complications and ensure therapeutic
effectiveness.
4. Monitoring and Assessment: Pharmacology knowledge helps nurses monitor patients
for therapeutic effects and adverse reactions, enabling early intervention when issues
arise.
5. Dosage Calculations: Nurses often calculate drug dosages, especially for pediatric and
critical care patients. Pharmacology skills ensure precise calculations to avoid overdosing
or underdosing.
6. Patient Advocacy: Nurses act as advocates by questioning unclear prescriptions,
reporting medication errors, and ensuring patients receive the best pharmacological care.

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 7. Contribution to Care Plans: Pharmacology knowledge helps nurses collaborate with
healthcare teams to design and adjust individualized care plans based on medication
effects and patient responses.
8. Specialized Nursing Practice: In areas such as critical care, oncology, or psychiatric
nursing, advanced pharmacology knowledge is essential for managing complex
medication regimens.
Pharmacology is a cornerstone of nursing practice. It equips nurses with the knowledge and
skills needed to ensure medication safety, promote patient well-being, and contribute effectively
to healthcare teams.

Definition, scope, terminologies and abbreviations used in pharmacology

1. Definition of Pharmacology:
Pharmacology is the branch of science that studies drugs, their origins, chemical properties,
mechanisms of action, therapeutic uses, and effects on living organisms. Pharmacology is the
science of drugs and medications, including a substance's origin, composition, pharmacokinetics,
pharmacodynamics, therapeutic use, and toxicology. It focuses on understanding how drugs
interact with biological systems to treat, prevent, or diagnose diseases.
 Key Terms:
o Drug: Any chemical substance that causes a change in a biological system.
o Pharmacokinetics: Study of drug absorption, distribution, metabolism, and
excretion (what the body does to the drug).
o Pharmacodynamics: Study of the biochemical and physiological effects of drugs
and their mechanisms of action (what the drug does to the body).

2. Scope of Pharmacology:
Pharmacology plays a significant role in healthcare and nursing practice. Its scope includes:
 Clinical Pharmacology: Study of drugs in humans, including drug trials and therapeutic
applications.
 Pharmacotherapy: Use of drugs to treat diseases and relieve symptoms.
 Toxicology: Study of harmful effects of drugs and other chemicals.
 Pharmacogenomics: How genetic variation affects drug response.
 Pharmaceutical Chemistry: Design and chemical properties of drugs.
 Pharmacy Practice: Dispensing medications and patient counseling.
3. Common Pharmacology Terminologies:
 Adverse Drug Reaction (ADR): An unintended and harmful reaction to a drug.
 Bioavailability: The fraction of an administered drug that reaches systemic circulation.
 Half-Life (t½): Time taken for the plasma concentration of a drug to reduce by half.
 Contraindication: A condition in which a drug should not be used.
 Potency: The amount of drug required to produce a therapeutic effect.
 Efficacy: The maximum effect a drug can produce.
4. Common Pharmacology Abbreviations:
 PO: By mouth (oral)
 IM: Intramuscular
 IV: Intravenous
 SC/SQ: Subcutaneous

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  PRN: As needed
 OD: Once daily
 BID: Twice daily
 TID: Three times daily
 QID: Four times daily
 HS: At bedtime
 STAT: Immediately
 AC: Before meals
 PC: After meals

GENERAL INFORMATION ABOUT DRUGS

Sources of drugs
Drugs are substances or compounds that prevent, treat, diagnose, or cure various conditions or
diseases. As mentioned previously, drugs come from a variety of resources—plants, animal
products, and inorganic substances. Ideally, these chemicals have desirable therapeutic effects
without harmful properties, although many derivatives may have poisonous effects, depending
upon the dosage used.
Both traditional and orthodox sources of drugs contribute significantly to modern medicine.
While traditional sources provide a foundation for many discoveries, orthodox approaches ensure
drug safety, efficacy, and consistency through scientific validation.
1. Traditional Sources of Drugs
Traditional medicine relies on natural sources, cultural practices, and historical knowledge
passed down through generations.
a. Plant Sources:
o Many drugs are derived from plants.
o Example: Digoxin (from Digitalis plant), Morphine (from Opium poppy).
b. Animal Sources:
o Some medications are obtained from animal tissues or secretions.

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 o Example: Insulin (originally derived from animal pancreas), Heparin (from pig
intestines).
c. Mineral Sources:
o Certain minerals are used directly or refined for medicinal use.
o Example: Iron (for anemia), Magnesium sulfate (as a laxative).
d. Microbial Sources:
o Microorganisms produce drugs through fermentation processes.
o Example: Penicillin (from Penicillium mold), Streptomycin (from Streptomyces
bacteria).
e. Marine Sources:
o Marine plants and animals are increasingly being explored for drug discovery.
o Example: Ziconotide (from marine snail venom).

2. Orthodox Sources of Drugs

Orthodox medicine relies on scientific research, laboratory synthesis, and clinical trials to
produce drugs.
a. Synthetic Drugs:
o Chemically manufactured in laboratories.
o Example: Aspirin (synthetically derived from salicylic acid), Ibuprofen.
b. Semi-Synthetic Drugs:
o Partially derived from natural sources but modified chemically.
o Example: Amoxicillin (derived from Penicillin).
c. Biotechnology and Genetic Engineering:
o Recombinant DNA technology produces drugs.
o Example: Recombinant Insulin, Monoclonal antibodies.
d. Radiopharmaceuticals:
o Radioactive substances used for diagnosis or therapy.
o Example: Iodine-131 (for thyroid disorders).
e. Nanotechnology:
o Drugs developed at a molecular level for targeted therapy.
o Example: Doxil (liposomal doxorubicin).

Biologics
Several medications, such as vaccines, antivenins and antitoxins, hormones, and monoclonal
antibodies, are known as biologics. Biologics are medications that come from a living source and
are developed through a combination of biomolecular science, immunology, and genetic
engineering. They show great promise in treating some cancers and other conditions that
currently have no available treatments. Biologics offer the advantage of more targeted therapy
for specific diseases, such as autoimmune disorders and cancer, with the potential for fewer side
effects, but they are uniquely formulated with complex pharmacotherapy and may require
administration through infusions or injections, which adds to the cost of treatment. Monoclonal
antibodies, exemplified by etanercept (Enbrel), a biologic, have revolutionized the treatment of
diseases like rheumatoid arthritis (RA). Formerly managed with drugs like methotrexate and
corticosteroids, known for their severe adverse effects, monoclonal antibodies now offer a more

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favorable and less toxic treatment option for RA. One of the primary drawbacks to the use of
biologics is their expense.

Chemical, Generic and Brand names.

There are three basic methods for identifying a drug—the chemical name, the generic name, and
the brand name, or trade name. If more than one drug company supplies a drug to the market,
then that drug will have more than one brand name.

Chemical Name:
The chemical name describes the drug's exact molecular structure and chemical composition. It
follows the rules of chemical nomenclature set by the International Union of Pure and
Applied Chemistry (IUPAC). Example: Acetylsalicylic Acid (Chemical name for Aspirin).
It is complex and difficult to remember and primarily used by chemists and researchers. Not
commonly used in clinical practice.

Generic Name:
The generic name is the official, non-proprietary name of the drug. It is assigned by
international drug regulatory authorities, such as the World Health Organization (WHO).
Generic names are universally accepted and provide a standard way to identify drugs.
Example: Ibuprofen (Generic name for Advil).
It is simpler and easier to remember than chemical names and often indicates the drug class (e.g.,
drugs ending in -olol are beta-blockers). Used in prescribing and clinical communication. The
same generic drug can be sold under multiple brand names.

Brand (Trade) Name:

The brand name is the proprietary or trademarked name given by the pharmaceutical
company that manufactures and markets the drug. Brand names are often more marketable,
catchy, and easy to remember. Example: Panadol (Brand name for Paracetamol).
It is exclusive to the pharmaceutical company and often varies between countries. It is protected
by patents for a specific duration and usually more expensive than generic versions.

Prescription and Over-the-Counter (OTC) Drugs

Both Prescription Drugs and OTC Drugs play essential roles in healthcare. Prescription drugs
address more serious conditions under professional supervision, while OTC drugs provide
convenient relief for minor health issues. Nurses must ensure patients understand the proper use
of both to prevent complications and promote safe medication practices.

1. Prescription Drugs
These are medications that require a written order (prescription) from a licensed healthcare
provider, such as a doctor. They are used for conditions requiring medical supervision due to
potential risks, side effects, or the need for dosage adjustments.

Key Characteristics:

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  Regulation: Strictly regulated by authorities like the Food and Drug Administration
(FDA).
 Usage: Intended for specific patients and conditions.
 Availability: Dispensed only by licensed pharmacists.
 Monitoring: Often require regular follow-ups to monitor effectiveness and side effects.
Examples:
 Antibiotics (e.g., Amoxicillin)
 Antihypertensives (e.g., Lisinopril)
 Opioid Pain Relievers (e.g., Morphine)

2. Over-the-Counter (OTC) Drugs

These are medications that can be purchased without a prescription directly from pharmacies,
supermarkets, or retail stores. They are considered safe for self-medication when used
according to the instructions on the label.
Key Characteristics:
 Regulation: Approved by regulatory bodies (e.g., FDA) for general public use.
 Usage: Treat minor ailments like headaches, colds, and allergies.
 Availability: Widely available in retail outlets.
 Safety: Generally have a wide margin of safety and minimal risk of misuse.
Examples:
 Pain Relievers (e.g., Paracetamol, Ibuprofen)
 Antacids (e.g., Ranitidine)
 Cough Syrups (e.g., Dextromethorphan)

Classification and Composition of Drugs

Drugs can be classified based on various criteria, including their therapeutic use, chemical
structure, mechanism of action, and legal status. Additionally, understanding the composition of
drugs helps in determining their effectiveness, safety, and potential side effects.

1. Classification of Drugs
A. Based on Therapeutic Use:
 Analgesics: Relieve pain (e.g., Paracetamol, Ibuprofen).
 Antibiotics: Treat bacterial infections (e.g., Amoxicillin, Ciprofloxacin).
 Antihypertensives: Control high blood pressure (e.g., Lisinopril, Amlodipine).
 Antidiabetics: Manage blood sugar levels (e.g., Metformin, Insulin).
B. Based on Chemical Structure:
 Steroids: Hormone-like drugs (e.g., Prednisone).
 Alkaloids: Derived from plants (e.g., Morphine, Atropine).
 Glycosides: Found in plants (e.g., Digoxin).
C. Based on Mechanism of Action:
 Beta-Blockers: Block beta-adrenergic receptors (e.g., Propranolol).
 Calcium Channel Blockers: Prevent calcium entry into cells (e.g., Nifedipine).
 ACE Inhibitors: Block angiotensin-converting enzyme (e.g., Lisinopril).
D. Based on Legal Status:
 Prescription Drugs: Require a doctor’s prescription (e.g., Antibiotics).
 Over-the-Counter (OTC) Drugs: Available without prescription (e.g., Paracetamol).

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  Controlled Substances: Strictly regulated due to abuse potential (e.g., Morphine).
E. Based on Origin:
 Natural Drugs: Derived from plants, animals, or minerals (e.g., Digitalis, Insulin).
 Synthetic Drugs: Man-made in laboratories (e.g., Ibuprofen).
 Semi-Synthetic Drugs: Chemically modified natural substances (e.g., Amoxicillin).

2. Composition of Drugs
Drugs are composed of two main components:
A. Active Pharmaceutical Ingredient (API):
 The API is the chemical compound responsible for the drug's therapeutic effect.
 Example: Paracetamol in fever-reducing medications.
B. Excipients:
 These are inactive substances added to the drug formulation to support the delivery and
effectiveness of the API.
 Functions of Excipients:
o Enhance drug stability.
o Improve taste and appearance.
o Aid in drug absorption.
o Provide bulk to the formulation.
 Examples:
o Binders: Ensure tablet cohesion (e.g., Starch).
o Fillers: Add bulk to tablets (e.g., Lactose).
o Preservatives: Prevent microbial growth (e.g., Benzalkonium chloride).

3. Common Drug Formulations Based on Composition:

 Tablets: Solid dosage form containing API and excipients (e.g., Aspirin tablet).
 Capsules: Gelatin shells containing powdered or liquid API (e.g., Amoxicillin capsule).
 Solutions: Liquid preparations (e.g., Cough syrup).
 Injections: Sterile solutions for direct administration (e.g., Insulin injection).
 Creams and Ointments: Semi-solid forms for topical application (e.g., Hydrocortisone
cream).

Introduction to the National Drug Policy and Essential Drug List in Nigeria
1. National Drug Policy (NDP) in Nigeria
The National Drug Policy (NDP) is a comprehensive framework developed by the Nigerian
government to ensure equitable access to safe, effective, affordable, and high-quality
medicines for all citizens. It serves as a guide for drug management, regulation, and distribution
across the country. Introduction of Nigeria’s First National Drug Policy, focusing on drug
availability and distribution was in 1988.

Objectives of the National Drug Policy:

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 1. Accessibility: Ensure essential medicines are available and affordable in all healthcare
facilities.
2. Quality Assurance: Guarantee that all drugs meet approved safety, efficacy, and quality
standards.
3. Rational Drug Use: Promote proper prescribing, dispensing, and use of medicines.
4. Local Drug Production: Encourage domestic manufacturing of pharmaceuticals to
reduce dependency on imports.
5. Pharmacovigilance: Monitor drug safety and report adverse drug reactions.
6. Research and Development: Support research on local medicinal plants and innovative
therapies.
7. Regulatory Control: Strengthen drug regulation through agencies like NAFDAC
(National Agency for Food and Drug Administration and Control).
8. Human Resource Development: Train healthcare professionals in pharmacology,
prescribing practices, and drug management.

Key Agencies Involved in Implementing the NDP:

 Federal Ministry of Health (FMoH)
 NAFDAC (National Agency for Food and Drug Administration and Control)
 PCN (Pharmacists Council of Nigeria)
 NDLEA (National Drug Law Enforcement Agency)

2. Essential Drug List (EDL) in Nigeria

The Essential Drug List (EDL) is a government-approved list of medications considered vital
for addressing the most common health issues in Nigeria. It aligns with the World Health
Organization (WHO) Model List of Essential Medicines and is periodically reviewed to
reflect changing health needs. Introduction of Nigeria's First Essential Drug List following WHO
guidelines was in 1989.

Objectives of the Essential Drug List:

1. Availability: Ensure continuous supply of essential medicines at all healthcare levels.
2. Affordability: Reduce costs and ensure medicines are economically accessible.
3. Appropriate Use: Promote rational prescribing, dispensing, and administration of
essential medicines.
4. Equity: Guarantee fair distribution of essential medicines across rural and urban areas.
Criteria for Selection of Drugs on the EDL:
 Proven efficacy, safety, and quality.
 Ability to address priority health conditions.
 Cost-effectiveness.
 Adequate evidence from clinical trials.
 Suitability for the Nigerian healthcare system.
Examples of Drugs on Nigeria's Essential Drug List:
 Analgesics: Paracetamol, Ibuprofen
 Antimalarials: Artemisinin-based Combination Therapy (ACT)
 Antibiotics: Amoxicillin, Ciprofloxacin
 Vaccines: BCG, Polio, Measles

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3. Importance of the National Drug Policy and Essential Drug List:
 Improved Healthcare Delivery: Ensures reliable access to life-saving medicines.
 Cost-Effective Healthcare: Reduces financial burden on patients and the healthcare
system.
 Drug Regulation: Prevents counterfeit and substandard drugs from entering the market.
 Rational Drug Use: Promotes responsible prescribing and reduces drug resistance.
 Healthcare Equity: Ensures rural and underserved areas have access to essential
medicines.

4. Challenges in Implementation:
 Poor Funding: Inadequate financial resources for drug procurement.
 Corruption: Diversion of essential drugs for personal profit.
 Weak Infrastructure: Poor logistics and storage facilities.
 Limited Local Production: Over-reliance on imported drugs.
 Public Awareness: Lack of knowledge about rational drug use among healthcare
providers and patients.

Preparation and Administration of drugs

Preparation of Drugs: Traditional and Orthodox
The preparation of drugs can be broadly categorized into Traditional and Orthodox methods,
reflecting differences in sources, techniques, and standardization.
1. Traditional Drug Preparation
Traditional drug preparation involves the use of natural sources such as plants, animals, and
minerals to prepare medicines based on indigenous knowledge and cultural practices, often
passed down through generations. It utilizes natural resources (plants, roots, leaves, bark,
animal products, minerals) and it is based on cultural heritage and oral traditions. Preparation
methods are often crude and unstandardized and it has limited scientific validation and
documentation. Commonly used in rural and underserved communities.
Methods of Traditional Drug Preparation:
1. Decoction: Boiling plant parts in water to extract active compounds (e.g., Neem leaves
for malaria).
2. Infusion: Soaking plant parts in hot or cold water (e.g., Ginger tea for cold relief).
3. Maceration: Soaking plant materials in water or alcohol for a prolonged period (e.g.,
Aloe vera extracts).
4. Powdering: Drying and grinding plant parts into powder (e.g., Turmeric powder).
5. Topical Applications: Preparing pastes or ointments for skin diseases (e.g., Shea butter
for burns).

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2. Orthodox Drug Preparation
Orthodox drug preparation refers to the scientific and industrial methods of drug formulation,
involving advanced technology, strict regulations, and standardized procedures to ensure safety,
efficacy, and quality. It is based on scientific research and clinical trials and highly regulated
by agencies like NAFDAC and WHO. It has precise dosage forms and administration
guidelines and manufactured in controlled environments (pharmaceutical industries) with
rigorous quality control and assurance measures.

Methods of Orthodox Drug Preparation:

1. Extraction and Isolation: Identifying and isolating active ingredients from natural or
synthetic sources.
2. Synthesis: Creating drugs chemically in laboratories (e.g., Ibuprofen).
3. Formulation: Combining active ingredients with excipients to create dosage forms (e.g.,
tablets, capsules, syrups).
4. Sterilization: Ensuring drug products are free from microbes (e.g., Injectable drugs).
5. Packaging: Proper labeling and sealing to ensure safety and prevent contamination.

WESTERN DELTA UNIVERSITY, OGHARA

BACHELOR OF NURSING SCIENCE
LECTURE NOTES PREPARED BY PROF IGHODARO IGBE

INTRODUCTION TO PHARMACOLOGY I
Course Code: PHM 301
Placement: 300 Level, First Semester
Duration: 30 hours lectures
Credit Unit: 2

DRUG ADMINISTRATION
Drug administration is the process of giving medications to a patient to achieve a desired
therapeutic effect. Proper drug administration is essential for maximizing drug efficacy,
minimizing adverse effects, and ensuring patient safety. The principles of drug administration
provide healthcare professionals with guidelines to ensure correct and safe medication use.

Principles of Drug Administration

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To ensure safe and effective medication administration, healthcare professionals follow specific
principles, often referred to as the "Rights of Drug Administration."

The "Five Rights" of Drug Administration

These five rights are essential to prevent medication errors:
1. Right Patient
o Verify the patient’s identity using at least two identifiers (e.g., name, date of birth,
medical record number).
o Avoid relying on room number or bed number.
2. Right Drug
o Ensure that the correct medication is administered.
o Double-check the drug name, concentration, and expiration date.
o Be aware of look-alike and sound-alike (LASA) medications.
3. Right Dose
o Administer the correct dosage as prescribed.
o Verify calculations, especially for pediatric and geriatric patients.
o Consider patient factors such as weight, age, and renal or hepatic function.
4. Right Route
o Administer the medication via the prescribed route (oral, intravenous,
intramuscular, etc.).
o Consider factors affecting absorption, bioavailability, and patient condition.
5. Right Time
o Administer the medication at the correct time and at the correct frequency.
o Consider food interactions and peak/trough levels for certain medications (e.g.,
antibiotics).
Classification of Routes of Drug Administration
Drug administration routes are classified into two main categories:
1. Enteral (via the gastrointestinal tract)
2. Parenteral (bypassing the gastrointestinal tract)
In addition, other specialized routes are used for localized or systemic effects.

1. Enteral Routes (Through the Gastrointestinal Tract)

Enteral administration involves drug absorption via the digestive tract.
(a) Oral (PO - Per Os)
 Definition: Drugs are swallowed and absorbed in the gastrointestinal (GI) tract.
 Common Forms: Tablets, capsules, syrups, suspensions.
 Advantages:
o Convenient and non-invasive.
o Safe and cost-effective.
o Suitable for self-administration.
 Disadvantages:
o Slow onset due to digestion and absorption.
o Subject to first-pass metabolism (drug breakdown in the liver before reaching
systemic circulation).
o Not suitable for unconscious, vomiting, or critically ill patients.

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  Examples: Paracetamol, ibuprofen, antibiotics.

(b) Sublingual (SL)

 Definition: Drugs are placed under the tongue and absorbed directly into the bloodstream
via the mucous membranes.
 Advantages:
o Rapid onset of action.
o Bypasses first-pass metabolism.
 Disadvantages:
o Limited to small, lipid-soluble drugs.
o Some drugs have an unpleasant taste.
 Examples: Nitroglycerin (for angina), buprenorphine.

(c) Buccal
 Definition: Drugs are placed between the cheek and gum for absorption.
 Advantages: Similar to sublingual, with direct absorption into the bloodstream.
 Disadvantages: Some drugs may cause irritation.
 Examples: Fentanyl buccal tablets, nicotine lozenges.

(d) Rectal (PR - Per Rectum)

 Definition: Drugs are administered via the rectum, usually as suppositories or enemas.
 Advantages:
o Useful for patients who cannot take oral medication (e.g., unconscious, vomiting
patients).
o Partial avoidance of first-pass metabolism.
 Disadvantages:
o Absorption can be unpredictable.
o Patient discomfort.
 Examples: Paracetamol suppositories, diazepam for seizures.

2. Parenteral Routes (Bypassing the GI Tract)

Parenteral routes involve the direct administration of drugs into the body, usually through
injections.
(a) Intravenous (IV)
 Definition: Drug is injected directly into a vein, entering systemic circulation
immediately.
 Advantages:
o Immediate onset of action.
o Precise control over drug levels.
o Suitable for emergency use.
 Disadvantages:
o Requires trained personnel.
o Risk of infections, phlebitis, and air embolism.
 Examples: IV antibiotics, chemotherapy, morphine.

(b) Intramuscular (IM)

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  Definition: Drug is injected into a muscle, typically the deltoid, gluteal, or thigh muscle.
 Advantages:
o Faster absorption than oral administration.
o Allows depot (slow-release) formulations.
 Disadvantages:
o Can be painful.
o Risk of nerve or vascular injury.
 Examples: Vaccines, penicillin, hormonal injections (e.g., Depo-Provera).

(c) Subcutaneous (SC or SQ)

 Definition: Drug is injected into the fatty tissue under the skin.
 Advantages:
o Slow, sustained absorption.
o Self-administration is possible.
 Disadvantages:
o Limited to small doses.
o Absorption may be affected by blood flow variations.
 Examples: Insulin, heparin, monoclonal antibodies.

(d) Intradermal (ID)

 Definition: Drug is injected into the dermis layer of the skin.
 Advantages:
o Used for diagnostic tests and immunizations.
 Disadvantages:
o Limited to small volumes.
 Examples: Tuberculosis (Mantoux) test, allergy testing.

3. Other Specialized Routes

Some routes are used for specific purposes to enhance drug effectiveness or minimize side
effects.
(a) Topical Route
 Definition: Drug is applied to the skin or mucous membranes for localized effects.
 Advantages:
o Direct action at the site of application.
o Reduced systemic side effects.
 Disadvantages:
o May cause local irritation.
 Examples: Corticosteroid creams, antifungal ointments, eye/ear drops.
(b) Transdermal Route
 Definition: Drug is absorbed through the skin into the bloodstream for systemic effects.
 Advantages:
o Long-acting, avoids first-pass metabolism.
o Convenient (e.g., patches).
 Disadvantages:
o Slow onset.
 Examples: Nicotine patches, fentanyl patches, hormone replacement patches.

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 (c) Inhalational Route
 Definition: Drugs are inhaled through the respiratory tract for systemic or local effects.
 Advantages:
o Rapid absorption via lung alveoli.
o Direct action on the lungs in respiratory diseases.
 Disadvantages:
o Requires proper inhalation technique.
o Can cause irritation.
 Examples: Asthma inhalers (salbutamol), anesthetic gases (isoflurane).

(d) Intrathecal Route

 Definition: Drug is injected into the cerebrospinal fluid (CSF) via the spinal cord.
 Advantages:
o Direct access to the central nervous system (CNS).
 Disadvantages:
o Requires skilled administration.
o Risk of complications like infections or bleeding.
 Examples: Epidural anesthesia, chemotherapy for CNS tumors.

(e) Intra-articular Route

 Definition: Drug is injected directly into a joint.
 Examples: Corticosteroids for arthritis.

Calculation of dosages: Tablets, lotions, solutions and infusions.

Accurate dosage calculations are crucial for ensuring patient safety and achieving the desired
therapeutic effects of medications. Errors in dosage calculations can lead to underdosing
(ineffective treatment) or overdosing (toxicity or adverse effects).

Dosage calculations vary based on the form of the drug, including:

 Tablets and Capsules (solid dosage forms)
 Lotions and Creams (topical applications)
 Solutions and Suspensions (liquids for oral or parenteral use)
 Infusions (intravenous fluids and medications)

1. Calculation of Tablet Dosages

Tablets and capsules are the most commonly used forms of medication. The required dose must
be adjusted based on the available strength of the drug.

Formula for Tablet Dosage Calculation

Example 1: Tablet Dosage Calculation

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Prescription: 500 mg of Paracetamol
Available: 250 mg tablets

Answer: The patient should take 2 tablets.

2. Calculation of Lotions and Creams

Lotions and creams are typically prescribed in percentage strength, indicating the amount of
active ingredient per 100 mL or 100 g.

Formula for Lotions/Creams

Example 3: Topical Lotion Calculation

Prescription: 2% Hydrocortisone cream, 50 g tube

Answer: The 50 g tube contains 1 g of hydrocortisone.

3. Calculation of Solutions (Oral and Injectable)

Liquid medications are measured in milliliters (mL) and typically expressed as mg/mL or
percentage solutions.

Formula for Oral and Injectable Solutions

Example 4: Oral Solution Calculation

Prescription: 250 mg Amoxicillin
Available: 125 mg/5 mL suspension

Answer: The patient should take 10 mL of the suspension.

Example 5: Injectable Solution Calculation

Prescription: 80 mg of Furosemide
Available: 20 mg/mL injection

Answer: The patient should receive 4 mL of the injection.

5. Calculation of Intravenous (IV) Infusions

IV infusions require precise calculations to determine the flow rate, usually expressed in
mL/hour or drops per minute (gtt/min) using a drip factor.
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Formula for IV Flow Rate in mL/hour

Example 6: IV Infusion Calculation

Prescription: 1000 mL Normal Saline over 8 hours

Answer: The infusion should be administered at 125 mL/hour.

Formula for IV Drip Rate (Drops per Minute - gtt/min)

Example 7: IV Drip Rate Calculation

Prescription: 500 mL Dextrose over 4 hours, drip factor 20 gtt/mL

Answer: The infusion should run at 42 drops per minute.

Common Errors in Dosage Calculations
1. Misinterpretation of prescriptions (e.g., mg vs. mcg, mL vs. L).
2. Incorrect conversions (e.g., 1 g = 1000 mg, 1 mL = 1000 mcL).
3. Failure to round correctly (e.g., rounding IV drip rates to whole numbers).
4. Not checking drug concentrations carefully before administration.
5. Ignoring patient-specific factors such as weight-based dosing for pediatric or critical
care patients.

Handling and Storage of Drugs

Proper handling and storage of drugs are essential to ensure their efficacy, safety, and stability.
Incorrect storage conditions can lead to drug degradation, reduced potency, and potential harm to
patients. Healthcare professionals must adhere to guidelines provided by manufacturers,
regulatory bodies, and best practices to maintain drug integrity.
General Principles of Drug Handling
Handling medications safely involves proper storage, preparation, dispensing, and administration
while minimizing contamination, degradation, and medication errors. The following are key
principles:
1. Maintain Hygiene and Safety – Always wash hands before handling medications to
prevent contamination. Use gloves and masks when necessary.
2. Follow Manufacturer Guidelines – Store and handle drugs as per the specifications
provided in the drug information leaflet.
3. Prevent Contamination – Avoid touching tablets and capsules directly with hands. Use
clean equipment for liquid medications.
4. Check Expiry Dates – Expired drugs may be ineffective or harmful and should be
disposed of properly.

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 5. Prevent Cross-Contamination – Keep different drug categories separate (e.g.,
antibiotics, cytotoxic drugs, vaccines).
6. Labeling – Ensure all drugs are correctly labeled with names, dosages, expiration dates,
and storage instructions.
7. Documentation and Record-Keeping – Maintain accurate records of drug receipt,
usage, and disposal.

Storage Conditions for Medications

Drugs must be stored under appropriate conditions to maintain their effectiveness. Key factors
affecting drug storage include:
1. Temperature Requirements
 Room Temperature (15–25°C) – Most solid medications, such as tablets and capsules,
are stored at room temperature.
 Refrigerated (2–8°C) – Vaccines, insulin, and certain liquid antibiotics require
refrigeration.
 Frozen (-20°C or lower) – Some biologics and specialty medications require freezing.
2. Protection from Light
 Light-sensitive drugs (e.g., nitroglycerin, some antibiotics, and vitamins) should be stored
in amber-colored bottles or opaque containers.
 Exposure to light can cause chemical degradation, reducing drug potency.
3. Humidity Control
 Avoid storing drugs in humid environments like bathrooms or kitchens, as moisture
can degrade tablets and capsules.
 Use desiccants (silica gel packets) to absorb excess moisture in medication containers.
3. Segregation of Medications
 Controlled Substances – Stored in locked cabinets with restricted access.
 Cytotoxic and Hazardous Drugs – Should be handled with protective equipment and
stored in designated areas.
 Flammable Drugs – Kept away from heat and ignition sources.
 Look-Alike/Sound-Alike (LASA) Drugs – Clearly labeled to prevent medication errors.

Specific Guidelines for Different Drug Forms

1 Tablets and Capsules
 Store in dry, cool places away from heat and humidity.
 Keep in original containers to prevent contamination.
 Avoid crushing unless explicitly allowed, as some drugs are enteric-coated or sustained-
release formulations.
2 Liquid Medications (Oral Syrups, Suspensions, and Injectable Solutions)
 Shake suspensions well before use.
 Refrigerate certain antibiotics after reconstitution (e.g., amoxicillin suspension).
 Avoid freezing liquid medications, as this may alter drug effectiveness.
3 Insulin and Biological Products
 Refrigeration is required (2–8°C), but should not be frozen.
 Opened insulin vials/pens can be stored at room temperature for up to 28 days.
 Check for changes in appearance (e.g., cloudiness, clumping) before use.
4 Vaccines

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  Stored in temperature-monitored refrigerators between 2–8°C.
 Must not be frozen unless specified.
 Cold chain management is essential to maintain vaccine potency.
5 Injectable Medications
 Some injections require protection from light (e.g., amphotericin B, furosemide).
 Once reconstituted, many injectable drugs have a limited stability period before they
must be discarded.
6 Ophthalmic and Otic Medications (Eye and Ear Drops)
 Keep sterile and discard 28 days after opening unless otherwise stated.
 Store in a cool place and avoid contamination of the dropper tip.
The handling of medications is subject to strict legal and regulatory requirements to ensure
patient safety, drug efficacy, and proper use. Healthcare professionals, including nurses,
midwives, and pharmacists, must comply with national and international legal frameworks
governing drug storage, administration, and record-keeping. Failure to adhere to these
regulations can lead to legal consequences, including loss of licensure, fines, or criminal
charges.

WESTERN DELTA UNIVERSITY, OGHARA

BACHELOR OF NURSING SCIENCE
LECTURE NOTES PREPARED BY PROF IGHODARO IGBE

INTRODUCTION TO PHARMACOLOGY I

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Course Code: PHM 301
Placement: 300 Level, First Semester
Duration: 30 hours lectures
Credit Unit: 2
DRUG OVERDOSE AND USE OF ANTIDOTES
Drug overdose occurs when an individual consumes a toxic or life-threatening amount of a
substance, leading to severe physiological disturbances or death. Overdoses can be accidental or
intentional and may involve prescription medications, illicit drugs, or household chemicals.
Nurses play a critical role in the early identification, management, and prevention of drug
overdose cases.
Types of drug overdoses
 Acute Overdose: A single excessive dose leading to immediate toxic effects.
 Chronic Overdose: Prolonged use of a substance leading to cumulative toxicity.

Drug toxicity and overdoses are serious medical emergencies that demand immediate and
effective treatment. Antidotes are specific substances used to neutralize the effects of poisons,
including drugs. They help reverse toxic effects, prevent severe complications, and save lives.

What is an Antidote?
An antidote is a substance that can neutralize or counteract the harmful effects of a poison or
toxin. It can work through various mechanisms, such as binding to the toxin, preventing its
absorption, enhancing its elimination, or reversing its physiological effects. The appropriate use
of antidotes is important in the management of poisoning cases and health practitioners must be
well-versed in their indications, administration, and mechanisms of action.

How does an Antidote work?

Antidotes work through various mechanisms to counteract the effects of toxins or poisons in the
body. Here’s a general overview of how antidotes work:

1. Neutralization.
Some antidotes directly neutralize the toxic substance by chemically reacting with it to form a
less harmful or inert compound. For example, antacids like calcium carbonate can neutralize
acidic substances.

2. Chelation.
Chelating agents bind to metal ions, such as heavy metals, in the body to form stable complexes
that can be excreted in the urine. This helps remove toxic metals from the body. Examples
include EDTA for lead poisoning and dimercaprol (BAL) for heavy metal poisoning.

3. Enhanced Elimination.
Certain antidotes enhance the elimination of toxins from the body by increasing their excretion
through urine, bile, or other routes. For instance, activated charcoal adsorbs toxins in the
gastrointestinal tract, preventing their absorption and facilitating their elimination via feces.

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4. Receptor Blockade.
Some antidotes work by blocking the action of toxins at specific receptors in the body. For
example, flumazenil blocks benzodiazepine receptors, reversing sedation and respiratory
depression caused by benzodiazepine overdose.

5. Antagonism.
Antagonistic antidotes counteract the effects of toxins by opposing their actions directly. For
example, vitamin K antagonizes the anticoagulant effects of warfarin by promoting the synthesis
of clotting factors.

6. Metabolic Conversion.
Certain antidotes facilitate the metabolism of toxins into less toxic metabolites or promote the
conversion of toxic substances into more easily eliminated forms. For example, acetylcysteine
facilitates the metabolism of acetaminophen into non-toxic metabolites in cases of
acetaminophen overdose.

TABLE OF COMMON ANTIDOTES

Toxin/Drug Antidote Mechanism of Action
Naloxone competitively binds to opioid
Opioids (e.g., Morphine) Naloxone receptors, reversing the effects of opioids
like respiratory depression and sedation.
Flumazenil competitively inhibits
benzodiazepine binding at the GABA
Benzodiazepines Flumazenil
receptor, reversing sedation and respiratory
depression.
Acetylcysteine replenishes glutathione
Acetaminophen N-Acetylcysteine stores, enhancing the non-toxic metabolism
(paracetamol) (NAC) of acetaminophen, thereby preventing liver
damage.
Aspirin (Salicylates) Sodium bicarbonate Urine alkalinization
Tricyclic Antidepressants Sodium bicarbonate Stabilizes cardiac function
Fomepizole inhibits alcohol
dehydrogenase, preventing the metabolism
Methanol, Ethylene Glycol Fomepizole, Ethanol
of toxic alcohols into their harmful
metabolites.
Atropine, Pralidoxime Blocks muscarinic receptors, reactivates
Organophosphates
(2-PAM) acetylcholinesterase
Dimercaprol chelates heavy metals,
Heavy Metals (Lead, Dimercaprol, EDTA, forming stable complexes that can be
Arsenic) Succimer excreted in the urine, thereby reducing
their toxicity.
Hydroxocobalamin,
Cyanide Detoxifies cyanide
Sodium Thiosulfate

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 Administering high-flow oxygen helps to
rapidly displace carbon monoxide from
100% Oxygen,
Carbon Monoxide (CO) hemoglobin, restoring oxygen delivery to
Hyperbaric Oxygen
tissues and reducing the risk of tissue
hypoxia and organ damage.
Various oral poisonings and
Activated charcoal adsorbs toxins in the
overdoses except for
Activated charcoal gastrointestinal tract, reducing their
cyanide, iron, lithium,
systemic absorption.
caustics, and alcohol.
Protamine sulfate binds to heparin, forming
Heparin overdose Protamine sulfate a stable complex that neutralizes its
anticoagulant effect.
Beta-blockers overdose, Glucagon increases cyclic AMP in cardiac
calcium channel blockers Glucagon cells, improving heart contractility and
overdose, hypoglycemia counteracting the effects of beta-blockers.

DRUG ABUSE AND ADDICTION: DEFINITION AND SCOPE

A. Definition
 Drug Abuse: The use of legal or illegal substances in a way that is harmful to the
individual or others. It often includes taking drugs in excessive amounts or for non-
medical reasons.
 Drug Addiction: A chronic, relapsing disorder characterized by compulsive drug-
seeking behavior, continued use despite harmful consequences, and long-term changes in
the brain.

B. Scope of Drug Abuse and Addiction

 Global Health Impact: Drug abuse contributes to major health issues, including
infectious diseases (HIV, hepatitis), mental disorders, and organ damage.
 Social and Economic Consequences: Increased crime rates, unemployment, and
financial burdens on families and healthcare systems.
 Commonly Abused Substances: Opioids, stimulants (cocaine, methamphetamine),
sedatives, hallucinogens, and alcohol.
Risk Factors:
o Genetic predisposition
o Mental health conditions such as depression and anxiety
o Peer pressure and social influences
o Socioeconomic factors, including poverty and lack of education
o Early exposure to drugs, particularly during adolescence
Effects of Drug Abuse and Addiction:
o Physical Effects: Organ damage (liver, kidney, heart), weakened immune system,
malnutrition.
o Psychological Effects: Depression, anxiety, paranoia, hallucinations.

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 o Behavioral Effects: Impaired judgment, risk-taking behavior, aggression,
withdrawal from social activities.
o Legal and Financial Consequences: Criminal charges, job loss, financial
instability.
Prevention and Treatment Strategies:
o Prevention:
 Public awareness campaigns and educational programs.
 Community engagement and early intervention.
 Prescription drug monitoring programs to prevent misuse.
 Strong family and peer support systems.
Treatment Approaches:
 Medical Treatments: Medication-assisted therapy (MAT) such as
methadone for opioid addiction.
 Behavioral Therapies: Cognitive-behavioral therapy (CBT), contingency
management, and motivational interviewing.
 Rehabilitation and Detoxification Centers: Structured environments for
recovery.
 Support Groups: Alcoholics Anonymous (AA) and Narcotics
Anonymous (NA).
PHARMACOKINETICS PRINCIPLES
Pharmacokinetic Phase
Pharmacokinetics refers to activities within the body after a drug is administered. These activities
include absorption, distribution, metabolism, and excretion (ADME). Another pharmacokinetic
component is the half-life of the drug. Half-life is a measure of the rate at which drugs are
removed from the body.

Absorption
Absorption follows administration and is the process by which a drug is made available for use
in the body. It occurs after dissolution of a solid form of the drug or after the administration of a
liquid or parenteral drug. In this process the drug particles within the gastrointestinal tract are
moved into the body fluids. This movement can be accomplished in several ways: active
absorption, passive absorption, and pinocytosis.
In active absorption a carrier molecule such as a protein or enzyme actively moves the drug
across the membrane. Passive absorption occurs by diffusion (movement from a higher
concentration to a lower concentration). In pinocytosis cells engulf the drug particle causing
movement across the cell. As the body transfers the drug from the body fluids to the tissue sites,
absorption into the body tissues occurs.
Several factors influence the rate of absorption, including the route of administration, the
solubility of the drug, and the presence of certain body conditions. Drugs are most rapidly
absorbed when given by the intravenous route, followed by the intramuscular route, the
subcutaneous route, and lastly, the oral route. Some drugs are more soluble and thus are absorbed
more rapidly than others. For example, water-soluble drugs are readily absorbed into the
systemic circulation. Bodily conditions, such as the development of lipodystrophy (atrophy of
the subcutaneous tissue) from repeated subcutaneous injections, inhibit absorption of a drug
given in the site of lipodystrophy

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Distribution
The systemic circulation distributes drugs to various body tissues or target sites. Drugs interact
with specific receptors during distribution. Some drugs travel by binding to protein (albumin) in
the blood. Drugs bound to protein are pharmacologically inactive. Only when the protein
molecules release the drug can the drug diffuse into the tissues, interact with receptors, and
produce a therapeutic effect.
As the drug circulates in the blood, a certain blood level must be maintained for the drugs to be
effective. When the blood level decreases below the therapeutic level, the drug will not produce
the desired effect. Should the blood level increase significantly over the therapeutic level, toxic
symptoms develop.

Metabolism
Metabolism, also called biotransformation, is the process by which a drug is converted by the
liver to inactive compounds through a series of chemical reactions. However, in some cases,
metabolites with potent biological activity or toxic properties are generated. Many of the enzyme
systems that transform drugs to inactive metabolites also generate biologically active metabolites
of endogenous compounds, as in steroid biosynthesis. Patients with liver disease may require
lower dosages of a drug detoxified by the liver, or the primary care provider may select a drug
that does not undergo a biotransformation by the liver. Frequent liver function texts are necessary
when liver disease is present. The kidneys, lungs, plasma, and intestinal mucosa also aid in the
metabolism of drugs.
Drug metabolism is divided into two phases. In phase I, enzymes such as cytochrome P450
oxidases introduce reactive or polar groups into xenobiotics. These modified compounds are then
conjugated to polar compounds in phase II reactions. Drug metabolism often converts lipophilic
compounds into hydrophilic products that are more readily excreted.

Excretion
The elimination of drugs from the body is called excretion. After the liver renders drugs inactive,
the kidney excretes the inactive compounds from the body. Also, some drugs are excreted
unchanged by the kidney without liver involvement. Patients with kidney disease may require a
dosage reduction and careful monitoring and lower dosages. Other drugs are eliminated by
sweat, breast milk, breath, or by the gastrointestinal tract in the feces

Half-Life
Half-life refers to the time required for the body to eliminate 50% of the drug. Knowledge of the
half-life of a drug is important in planning the frequency of dosing. For example, drugs with a
short half-life (2–4 hours) need to be administered frequently, whereas a drug with a long half-
life (21–24 hours) requires less frequent dosing. It takes five to six half-lives to eliminate
approximately 98% of a drug from the body. Although half-life is fairly stable, patients with liver
or kidney disease may have problems excreting a drug. Difficulty in excreting a drug increases
the half-life and increases the risk of toxicity. For example, digoxin (Lanoxin) has a long half-life
(36 hours) and requires once-daily dosing. However, aspirin has a short half-life and requires
frequent dosing. Older patients or patients with impaired kidney or liver function require
frequent diagnostic tests measuring renal or hepatic function.

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PHARMACODYNAMICS
Pharmacodynamics deals with the drug’s action and effect within the body. After administration,
most drugs enter the systemic circulation and expose almost all body tissues to possible effects of
the drug. All drugs produce more than one effect in the body. The primary effect of a drug is the
desired or therapeutic effect. Secondary effects are all other effects, whether desirable or
undesirable, produced by the drug. Most drugs have an affinity for certain organs or tissues and
exert their greatest action at the cellular level on those specific areas, which are called target
sites. There are two main mechanisms of action:
1. Alteration in cellular environment
2. Alteration in cellular function

Alteration in Cellular Environment

Some drugs act on the body by changing the cellular environment, either physically or
chemically. Physical changes in the cellular environment include changes in osmotic pressures,
lubrication, absorption, or the conditions on the surface of the cell membrane. An example of a
drug that changes osmotic pressure is mannitol, which produces a change in the osmotic pressure
in brain cells, causing a reduction in cerebral edema. A drug that acts by altering the cellular
environment by lubrication is sunscreen. An example of a drug that acts by altering absorption is
activated charcoal, which is administered orally to absorb a toxic chemical ingested into the
gastrointestinal tract. The stool softener docusate is an example of a drug that acts by altering the
surface of the cellular membrane. Docusate has emulsifying and lubricating activity that causes a
lowering of the surface tension in the cells of the bowel, permitting water and fats to enter the
stool. This softens the fecal mass, allowing easier passage of the stool. Chemical changes in the
cellular environment include inactivation of cellular functions or the alteration of the chemical
components of body fluid, such as a change in the pH. For example, antacids neutralize gastric
acidity in patients with peptic ulcers.

Alteration in Cellular Function

Most drugs act on the body by altering cellular function. A drug cannot completely change the
function of a cell, but it can alter its function. A drug that alters cellular function can increase or
decrease certain physiologic functions, such as increase heart rate, decrease blood pressure, or
increase urine output.

a. Receptor-Mediated Drug Action

The function of a cell alters when a drug interacts with a receptor cell. A receptor is a
specialized macromolecule (a large group of molecules linked together) that attaches or binds to
the drug molecule. This alters the function of the cell and produces the therapeutic response of
the drug. For a drug–receptor reaction to occur, a drug must be attracted to a particular receptor.
Drugs bind to a receptor much like a piece of a puzzle. The closer the shape, the better the fit,
and the better the therapeutic response. The intensity of a drug response is related to how good
the “fit” of the drug molecule is and the number of receptor sites occupied.
Agonists are drugs that bind with a receptor to produce a therapeutic response. Drugs that bind
only partially to the receptor will most probably have some, although slight, therapeutic
response.

25
Partial agonists are drugs that have some drug receptor fit and produce a response but inhibit
other responses.
Antagonists join with a receptor to prevent the action of an agonist. When the antagonist binds
more tightly than the agonist to the receptor, the action of the antagonist is strong. Drugs that act
as antagonists produce no pharmacologic effect. An example of an antagonist is Narcan, a
narcotic antagonist that completely blocks the effects of morphine, including the respiratory
depression. This drug is useful in reversing the effects of an overdose of narcotics.

b. Receptor-Mediated Drug Effects

The number of available receptor sites influences the effects of a drug. If only a few receptor
sites are occupied, although many sites are available, the response will be small. If the drug dose
is increased, more receptor sites are used and the response increases. If only a few receptor sites
are available, the response does not increase if more of the drug is administered. However, not all
receptors on a cell need to be occupied for a drug to be effective. Some extremely potent drugs
are effective even when the drug occupies few receptor site.

DRUG REACTIONS
Drugs produce many reactions in the body. The following sections discuss adverse drug
reactions, allergic drug reactions, drug idiosyncrasy, drug tolerance, cumulative drug effect, and
toxic reactions. Pharmacogenetic reactions can also occur. A pharmacogenetic reaction is a
genetically determined adverse reaction to a drug.

Adverse Drug Reactions

Patients may experience one or more adverse reactions (side effects) when they are given a drug.
Adverse reactions are undesirable drug effects. Adverse reactions may be common or may occur
infrequently. They may be mild, severe, or life threatening. They may occur after the first dose,
after several doses, or even after many doses. An adverse reaction often is unpredictable,
although some drugs are known to cause certain adverse reactions in many patients. For
example, drugs used in the treatment of cancer are very toxic and are known to produce adverse
reactions in many patients receiving them. Other drugs produce adverse reactions in fewer
patients. Some adverse reaction is predictable, but many adverse drug reactions occur without
warning.
Some texts use both terms side effect and adverse reactions. These texts distinguish between the
two terms by using side effects to explain mild, common, and nontoxic reactions; adverse
reaction is used to describe more severe and life-threatening reactions. For the purposes of this
text only the term adverse reaction is used, with the understanding that these reactions may be
mild, severe, or life threatening.

Allergic Drug Reactions

An allergic reaction also is called a hypersensitivity reaction. A drug allergy occurs because the
individual’s immune system views the drug as a foreign substance or antigen. The presence of an
antigen stimulates the antigen–antibody response that in turn prompts the body to produce
antibodies. If the patient takes the drug after the antigen–antibody response has occurred, an
allergic reaction result. Even a mild allergic reaction produces serious effects if it goes unnoticed
and the drug is given again.

26
Any indication of an allergic reaction is reported to the primary health care provider before the
next dose of the drug is given. Serious allergic reactions require contacting the primary health
care provider immediately because emergency treatment may be necessary. Some allergic
reactions occur within minutes (even seconds) after the drug is given; others may be delayed for
hours or days. Allergic reactions that occur immediately often are the most serious. Allergic
reactions are manifested by a variety of signs and symptoms observed by the nurse or reported
by the patient. Examples of some allergic symptoms include itching, various types of skin rashes,
and hives (urticaria). Other symptoms include difficulty breathing, wheezing, cyanosis, a sudden
loss of consciousness, and swelling of the eyes, lips, or tongue.
Anaphylactic shock is an extremely serious allergic drug reaction that usually occurs shortly
after the administration of a drug to which the individual is sensitive. This type of allergic
reaction requires immediate medical attention. Anaphylactic shock can be fatal if the symptoms
are not identified and treated immediately. Treatment is to raise the blood pressure, improve
breathing, restore cardiac function, and treat other symptoms as they occur.

Drug Idiosyncrasy
Drug idiosyncrasy is a term used to describe any unusual or abnormal reaction to a drug. It is any
reaction that is different from the one normally expected of a specific drug and dose. For
example, a patient may be given a drug to help him or her sleep (eg, a hypnotic). Instead of
falling asleep, the patient remains wide awake and shows signs of nervousness or excitement.
This response is an idiosyncratic response because it is different from what the nurse expects
from this type of drug. Another patient may receive the same drug and dose, fall asleep, and after
8 hours be difficult to awaken. This, too, is abnormal and describes an overresponse to the drug.
The cause of drug idiosyncrasy is not clear. It is believed to be due to a genetic deficiency that
makes the patient unable to tolerate certain chemicals, including drugs.

Pharmacogenetic Reactions
A pharmacogenetic disorder is a genetically determined abnormal response to normal doses of a
drug. This abnormal response occurs because of inherited traits that cause abnormal metabolism
of drugs. For example, individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency
have abnormal reactions to a number of drugs. These patients exhibit varying degrees of
hemolysis (destruction of red blood cells) if these drugs are administered. More than 100 million
people are affected by this disorder. Examples of drugs that cause hemolysis in patients with a
G6PD deficiency include aspirin, chloramphenicol, and the sulfonamides.

DRUG—DRUG INTERACTIONS
A drug–drug interaction occurs when one drug interacts with or interferes with the action of
another drug. For example, taking an antacid with oral tetracycline causes a decrease in the
effectiveness of the tetracycline. The antacid chemically interacts with the tetracycline and
impairs its absorption into the bloodstream, thus reducing the effectiveness of the tetracycline.
Drugs known to cause interactions include oral anticoagulants, oral hypoglycemics, anti-
infectives, antiarrhythmics, cardiac glycosides, and alcohol. Drug–drug interactions can produce
effects that are additive, synergistic, or antagonistic.

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Additive drug reaction. An additive drug reaction occurs when the combined effect of two
drugs is equal to the sum of each drug given alone. For example, taking the drug heparin with
alcohol will increase bleeding. The equation one + one = two is sometimes used to illustrate the
additive effect of drugs.

Synergistic drug reaction. Drug synergism occurs when drugs interact with each other and
produce an effect that is greater than the sum of their separate actions. The equation one + one =
four may be used to illustrate synergism. An example of drug synergism is when a person takes
both a hypnotic and alcohol. When alcohol is taken simultaneously or shortly before or after the
hypnotic is taken, the action of the hypnotic increases. The individual experiences a drug effect
that is greater than if either drug was taken alone. On occasion, the occurrence of a synergistic
drug effect is serious and even fatal.

Antagonistic drug reaction. An antagonistic drug reaction occurs when one drug interferes with
the action of another, causing neutralization or a decrease inthe effect of one drug. For example,
protamine sulfate is a heparin antagonist. This means that the administration of protamine sulfate
completely neutralizes the effects of heparin in the body.

DRUG—FOOD INTERACTIONS
When a drug is given orally, food may impair or enhance its absorption. A drug taken on an
empty stomach is absorbed into the bloodstream at a faster rate than when the drug is taken with
food in the stomach. Some drugs (eg, captopril) must be taken on an empty stomach to achieve
an optimal effect. Drugs that should be taken on an empty stomach are administered 1 hour
before or 2 hours after meals. Other drugs, especially drugs that irritate the stomach, result in
nausea or vomiting, or cause epigastric distress, are best given with food or meals. This
minimizes gastric irritation. The nonsteroidal anti-inflammatory drugs and salicylates are
examples of drugs that are given with food to decrease epigastric distress. Still other drugs
combine with a drug forming an insoluble food–drug mixture. For example, when tetracycline is
administered with dairy products, a drug–food mixture is formed that is unabsorbable by the
body. When a drug is unabsorbable by the body, no pharmacologic effect occurs.

FACTORS INFLUENCING DRUG RESPONSE

Certain factors may influence drug response and are considered when the primary health care
provider prescribes and the nurse administers a drug. These factors include age, weight, gender,
disease, and route of administration

Age
The age of the patient may influence the effects of a drug. Infants and children usually require
smaller doses of a drug than adults do. Immature organ function, particularly the liver and
kidneys, can affect the ability of infants and young children to metabolize drugs. An infant’s
immature kidneys impair the elimination of drugs in the urine. Liver function is poorly
developed in infants and young children. Drugs metabolized by the liver may produce more
intense effects for longer periods. Parents must be taught the potential problems associated with
administering drugs to their children. For example, a safe dose of a nonprescription drug for a 4-

28
year-old child may be dangerous for a 6-month-old infant. Elderly patients may also require
smaller doses, although this may depend on the type of drug administered. For example, the
elderly patient may be given the same dose of an antibiotic as a younger adult.
However, the same older adult may require a smaller dose of a drug that depresses the central
nervous system, such as a narcotic. Changes that occur with aging affect the pharmacokinetics
(absorption, distribution, metabolism, and excretion) of a drug. Any of these processes may be
altered because of the physiologic changes that occur with aging.
Polypharmacy is the taking of numerous drugs that can potentially react with one another. When
practiced by the elderly, polypharmacy leads to an increase in the number of potential adverse
reactions. Although multiple drug therapy is necessary to treat certain disease states, it always
increases the possibility of adverse reactions

Weight
In general, dosages are based on a weight of approximately 150 lb, which is calculated to be the
“average” weight of men and women. A drug dose may sometimes be increased or decreased
because the patient’s weight is significantly higher or lower than this average. With narcotics, for
example, higher or lower than average dosages may be necessary to produce relief of pain,
depending on the patient’s weight.

Gender
The gender of an individual may influence the action of some drugs. Women may require a
smaller dose of some drugs than men. This is because many women are smaller than men and
have a body fat-and-water ratio different from that of men. variation between male and female
are observed following puberty. Hence, sex related differences in the rate of metabolism maybe
due to sex hormones.

Disease
The presence of disease may influence the action of some drugs. Sometimes disease is an
indication for not prescribing a drug or for reducing the dose of a certain drug. Both hepatic
(liver) and renal (kidney) disease can greatly affect drug response. In liver disease, for example,
the ability to metabolize or detoxify a specific type of drug may be impaired. If the average or
normal dose of the drug is given, the liver may be unable to metabolize the drug at a normal rate.
Consequently, the drug may be excreted from the body at a much slower rate than normal. The
primary health care provider may then decide to prescribe a lower dose and lengthen the time
between doses because liver function is abnormal. Patients with kidney disease may exhibit drug
toxicity and a longer duration of drug action. The dosage of drugs may be reduced to prevent the
accumulation of toxic levels in the blood or further injury to the kidney.

Route of Administration
Intravenous administration of a drug produces the most rapid drug action. Next in order of time
of action is the intramuscular route, followed by the subcutaneous route. Giving a drug orally
usually produces the slowest drug action. Some drugs can be given only by one route; for

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example, antacids are given only orally. Other drugs are available in oral and parenteral forms.
The primary health care provider selects the route of administration based on many factors,
including the desired rate of action. For example, the patient with a severe cardiac problem may
require intravenous administration of a drug that affects the heart. Another patient with a mild
cardiac problem may experience a good response to oral administration of the same drug.

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