• Course Title: Pharmacodynamics and Chemotherapy I

• Credit Units and Contact Hours: 2 Units C: LH 30

• Year: 3
• Semester: 1
• Course Lecturer: R. S. BIDA
Module 1: Introduction to Pharmacodynamics and Drug Sources
• Classifications of drugs (chemical, generic, and trade names)

DRUG CLASSIFICATION BASED ON FUNCTION, FORMATION, AND

NOMENCLATURE

Drugs are classified using various criteria, including their therapeutic function, chemical structure, and naming
conventions. Understanding these classifications is essential for healthcare professionals to effectively and
safely prescribe, dispense, and administer medications.

Classification by Function

Drugs are primarily categorized based on their therapeutic effect or the physiological system they influence.
This functional classification provides a clear understanding of the drug's intended use and mechanism of action.

1. Analgesics: These drugs are designed to alleviate pain. They are broadly divided into two main
categories:
a. Opioid Analgesics: These drugs, such as morphine, codeine, and fentanyl, act on opioid
receptors in the brain and spinal cord to reduce the perception of pain. They are typically used
for moderate to severe pain.
b. Non-Opioid Analgesics: This group includes drugs like acetaminophen (paracetamol) and
nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and naproxen.
Acetaminophen primarily reduces pain and fever, while NSAIDs also have anti-inflammatory
properties.
2. Antibacterial: These medications combat bacterial infections by either killing bacteria (bactericidal) or
inhibiting their growth (bacteriostatic). Examples include:
a. Penicillins: Such as penicillin G and amoxicillin, which interfere with bacterial cell wall
synthesis.
NUM PHA 303 Classification of drugs 1|Page
 b. Cephalosporins: Like cephalexin and ceftriaxone, which also target bacterial cell walls.
c. Tetracyclines: Such as doxycycline, which inhibit bacterial protein synthesis.
3. Antihypertensives: These drugs are used to lower high blood pressure (hypertension). They work
through various mechanisms:
a. ACE Inhibitors (Angiotensin-Converting Enzyme Inhibitors): Such as lisinopril and
enalapril, which prevent the formation of angiotensin II, a substance that narrows blood vessels.
b. Beta-Blockers: Like metoprolol and atenolol, which block the effects of adrenaline on the heart,
slowing the heart rate and reducing blood pressure.
c. Calcium Channel Blockers: Such as amlodipine and diltiazem, which relax blood vessels,
allowing blood to flow more easily.
d. Diuretics: Such as hydrochlorothiazide and furosemide, which help the kidneys remove excess
sodium and water, reducing blood volume.
4. Antidepressants: These drugs are used to treat depression and other mood disorders. They work by
affecting the levels of neurotransmitters in the brain:
a. SSRIs (Selective Serotonin Reuptake Inhibitors): Such as fluoxetine (Prozac), sertraline
(Zoloft), and paroxetine (Paxil), which increase serotonin levels by preventing its reabsorption.
b. Tricyclic Antidepressants: Like amitriptyline and nortriptyline, which affect serotonin and
norepinephrine levels.
c. MAOIs (Monoamine Oxidase Inhibitors): Such as phenelzine and tranylcypromine, which
inhibit the enzyme monoamine oxidase, increasing the levels of serotonin, norepinephrine, and
dopamine.
5. Antidiabetics: These medications are used to manage diabetes mellitus. They work through various
mechanisms to control blood glucose levels:
a. Insulin: Used to replace or supplement the body's own insulin, particularly in type 1 diabetes.
Examples include insulin lispro, insulin aspart, and insulin glargine.
b. Metformin: A biguanide that reduces glucose production in the liver and improves insulin
sensitivity.
c. Sulfonylureas: Such as glipizide and glyburide, which stimulate the pancreas to release more
insulin.
d. SGLT2 Inhibitors (Sodium-Glucose Cotransporter 2 Inhibitors): Such as empagliflozin and
dapagliflozin, which increase glucose excretion in the urine.
6. Antiemetics: These drugs are used to prevent or treat nausea and vomiting. Examples include:
a. Ondansetron: A serotonin 5-HT3 receptor antagonist, often used to prevent chemotherapy-
induced nausea and vomiting.
NUM PHA 303 Classification of drugs 2|Page
 b. Promethazine: An antihistamine with antiemetic properties.
c. Metoclopramide: A dopamine antagonist and prokinetic agent.
7. Anticoagulants: These drugs prevent blood clot formation, reducing the risk of stroke, heart attack, and
other thromboembolic events. Examples include:
a. Warfarin: An oral anticoagulant that inhibits vitamin K-dependent clotting factors.
b. Heparin: An injectable anticoagulant that enhances the activity of antithrombin.
c. Direct Oral Anticoagulants (DOACs): Such as rivaroxaban and apixaban, which directly
inhibit specific clotting factors.

Drug Classification Based on Preparation

Drugs are classified not only by their therapeutic effects and chemical structures but also by their pharmaceutical
formulations, which dictate how they are administered and absorbed into the body.

The preparation of a drug significantly influences its bioavailability, onset of action, duration of effect, and
overall efficacy.

Solid Dosage Forms

Solid dosage forms are designed for oral administration and offer advantages such as ease of manufacturing,
accurate dosing, and stability.

1. Tablets: Tablets are the most common solid dosage form. They are prepared by compressing a mixture
of active pharmaceutical ingredients (APIs) and excipients (inactive ingredients) into a solid form.
Excipients can include binders (to hold the tablet together), disintegrants (to help the tablet break apart
in the gastrointestinal tract), lubricants (to aid in the manufacturing process), and fillers (to add bulk).
Tablets can be designed for immediate release, modified release (e.g., extended-release), or enteric
coating (to protect the drug from stomach acid). E.g. Paracetamol
2. Capsules: Capsules encapsulate the drug within a shell, typically made of gelatin or a plant-based
material. They can be hard capsules (containing powder, granules, or pellets) or soft capsules (containing
liquid or semi-solid formulations). Capsules offer advantages such as masking the taste of the drug,
protecting the drug from degradation, and providing a controlled release of the drug. E.g. Ampicillin

NUM PHA 303 Classification of drugs 3|Page

 3. Powders: Powders are finely divided solid particles of drugs, which can be administered orally (e.g.,
mixed with water), topically, or via inhalation. Powders are often used for drugs that are unstable in
liquid form or for formulations where rapid dissolution is desired. E.g. Diclofenac + potassium Powder
4. Granules: Granules are aggregates of powder particles, which improve flow properties and reduce dust
formation. They can be compressed into tablets or filled into capsules.

Liquid Dosage Forms

Liquid dosage forms are often preferred for patients who have difficulty swallowing solid dosage forms or when
rapid absorption is desired.

1. Solutions: Solutions are homogeneous mixtures where the drug is completely dissolved in a solvent,
such as water, alcohol, or a combination of solvents. Solutions offer rapid absorption and uniform
dosing.
2. Syrups: Syrups are concentrated solutions of sugar (e.g., sucrose) or sugar substitutes in water, often
containing flavouring agents and medicinal substances. They are palatable and suitable for paediatric
patients. Vitamin C syrup
3. Elixirs: Elixirs are clear, sweetened hydroalcoholic solutions, often containing flavouring agents. They
typically contain a lower concentration of sugar than syrups and may contain alcohol.
4. Suspensions: Suspensions are heterogeneous mixtures where the drug is dispersed as solid particles in
a liquid vehicle. Suspensions require shaking before administration to ensure uniform dosing. Ampiclox
5. Emulsions: Emulsions are mixtures of two immiscible liquids, such as oil and water, stabilized by an
emulsifying agent. They can be administered orally, topically, or intravenously.

Semi-Solid Dosage Forms

Semi-solid dosage forms are used for topical, rectal, or vaginal administration.

1. Ointments: Ointments are semisolid preparations containing a drug dissolved or dispersed in a greasy
base, such as petrolatum or lanolin. They are used for topical application to provide a protective barrier
and deliver the drug to the skin. E.g. penicillin ointment
2. Creams: Creams are semisolid emulsions of oil and water, containing a drug dissolved or dispersed in
the emulsion. They are less greasy than ointments and are easily spreadable. E.g. clotrimazole cream
3. Gels: Gels are semisolid systems consisting of a network of solid particles dispersed in a liquid. They
can be used for topical, nasal, or vaginal administration.

NUM PHA 303 Classification of drugs 4|Page

 4. Suppositories: Suppositories are solid dosage forms designed for insertion into the rectum, vagina, or
urethra. They melt or dissolve at body temperature, releasing the drug for local or systemic effects.

Other Dosage Forms

1. Inhalations: Inhalations are dosage forms administered via the respiratory tract. They can include
aerosols, metered-dose inhalers (MDIs), and dry powder inhalers (DPIs).
2. Injectables: Injectables are sterile solutions, suspensions, or emulsions administered parenterally (e.g.,
intravenously, intramuscularly, subcutaneously).
3. Transdermal Patches: Transdermal patches deliver drugs through the skin into the systemic
circulation. They provide a controlled and sustained release of the drug.

The classification of drugs based on their preparation is crucial for understanding how a drug will be
administered, absorbed, and distributed within the body. Each formulation has unique characteristics that
influence its therapeutic efficacy and safety profile.

Drug Nomenclature

The process of drug development involves complex chemical synthesis or extraction from natural sources. The
naming of drugs follows a structured system to ensure clarity and facilitate communication.

1. Chemical Name: This name describes the drug's complete chemical structure, including the
arrangement of atoms and functional groups. It is often complex and not commonly used in clinical
practice. For example, the chemical name for ibuprofen is 2-(4-isobutylphenyl) propanoic acid.
2. Generic Name (Non-proprietary Name): This is the official, non-proprietary name of the drug. It is a
universally recognized name that reflects the drug's chemical structure or pharmacological action.
Generic names are typically less complex than chemical names and are used by healthcare professionals
worldwide. For example, the generic name for diazepam is diazepam.
3. Brand Name/Trade Name (Proprietary Name): This is the name given to a drug by the
pharmaceutical company that manufactures it. Brand names are trademarked and can vary depending on
the country. The brand name for diazepam is Valium.

The relationship between these names is that a single drug has one chemical name, one generic name (in some
cases two), and can have multiple brand names depending on the manufacturer and the country where it is
marketed. This system allows for clear identification and communication about medications across different
settings and regions.
NUM PHA 303 Classification of drugs 5|Page
QUIZ

1. Give at least twenty (20) classification of drugs based on their function with appropriate examples.
2. Give at least ten (10) classification of drugs based on their formation/preparation with appropriate
examples.
3. Give examples of drugs with their chemical names, brand names and generic/ non-proprietary names.

NUM PHA 303 Classification of drugs 6|Page