PHARMACOLOGY

PART 1 Introduction to Nursing Pharmacology

1. Introduction to Drugs

 Pharmacology is the study of the biological effects of chemicals.

 Drugs are chemicals that are introduced into the body to cause some sort of change.
 Nurses deal with pharmacotherapeutics, or clinical pharmacology, the branch of pharmacology that
uses drugs to treat, prevent, and diagnose disease.
o Pharmacotherapeutics addresses two key concerns: the drug’s effects on the body and the
body’s response to the drug.
 The nurse is in a unique position regarding drug therapy because nursing responsibilities include the
following:
o Administering drugs
o Assessing drug effects
o Intervening to make the drug regimen more tolerable
o Providing patient teaching about drugs and the drug regimen
o Monitoring the overall patient care plan to prevent medication errors

SOURCES OF DRUGS
 Natural Sources - To become a drug, a chemical must have a demonstrated therapeutic value or
efficacy without severe toxicity or damaging properties.
 Plants - Plants and plant parts have been used as medicines since prehistoric times. Even
today, plants are an important source of chemicals that are developed into drugs.
 Animal Products - Animal products are used to replace human chemicals that fail to be
produced because of disease or genetic problems.
 Inorganic Compounds - Salts of various chemical elements can have therapeutic effects in
the human body. Aluminum, fluoride, iron, and even gold is used to treat various
conditions.
 Synthetic Sources - many drugs are developed synthetically after chemicals in plants, animals, or the
environment have been tested and found to have therapeutic activity. Scientists use genetic
engineering to alter bacteria to produce chemicals that are therapeutic and effective. Sometimes, a
small change in a chemical’s structure can make that chemical more useful as a drug—more potent,
more stable, and less toxic.
 DRUG EVALUATION
After a chemical that might have therapeutic value is identified, it must undergo a series of scientific
tests to evaluate its actual therapeutic and toxic effects. This process is tightly controlled by the Food
and Drug Administration (FDA), an agency of the U.S. Department of Health and Human Services that
regulates the development and sale of drugs.

Phases of Drug Development

 An approved drug is given a brand name (trade name) by the pharmaceutical company that
developed it.
 The generic name of a drug is the original designation that the drug was given when the drug

company applied for the approval process.

 Chemical names are names that reflect the chemical structure of a drug.

LEGAL REGULATION OF DRUGS

The FDA regulates the development and sale of drugs. Local laws further regulate the distribution and
administration of drugs. In most cases, the strictest law is the one that prevails. Nurses should become
familiar with the rules and regulations in the area in which they practice. These regulations can vary
from state to state, and even within a state.
 Generic drugs are drugs no longer protected by patent and can be produced by companies other
than the one that developed it.
 OTC (Over-the-counter) drugs are available without a prescription and are deemed safe when used
as directed.
 Orphan drugs are drugs that have been discovered but that are not financially viable because they
have a limited market or a narrow margin of safety.
 SOURCES OF DRUG INFORMATION
The fields of pharmacology and drug therapy change so quickly that it is important to have access to
sources of information about drug doses, therapeutic and adverse effects, and nursing-related
implications.
 Drug Labels - have specific information that identifies a specific drug. For example, a drug label
identifies the brand and generic names for the drug, the drug dosage, the expiration date, and
special drug warnings. Some labels also indicate the route and dose for administration.
 Package Inserts - All drugs come with a package insert prepared by the manufacturer according to
strict FDA regulations. The package insert contains all of the chemical and study information that led
to the drug’s approval.

 Reference Book - A wide variety of reference books are available for drug information.
o The Physician’s Desk Reference (PDR)
o Drug Facts and Comparisons
o AMA Drug Evaluation
o LNDG
 Journals - Various journals can be used to obtain drug information. For example, the Medical Letter
is a monthly review of new drugs, drug classes, and specific treatment protocols. The American
Journal of Nursing offers information on new drugs, drug errors, and nursing implications.
 Internet Information - Many patients now use the Internet as a source of medical information and
advice.
 2. Drugs and the Body
 Pharmacodynamics - study of the interactions between the chemical components of living systems
and the foreign chemicals, including drugs, that enter those systems.
 Drugs usually work in one of four ways:
1. To replace or act as substitutes for missing chemicals
2. To increase or stimulate certain cellular activities
3. To depress or slow cellular activities
4. To interfere with the functioning of foreign cells, such as invading microorganisms or
neoplasms (drugs that act in this way are called chemotherapeutic agents).
 Chemotherapeutic agents work by interfering with normal cell functioning, causing cell death. The
most desirable chemotherapeutic agents are those with selective toxicity to foreign cells and foreign
cell activities.
 Drugs frequently act at specific receptor sites on cell membranes to stimulate enzyme systems
within the cell and to alter the cell’s activities.
 Pharmacokinetics - the study of the way the body deals with drugs—includes absorption,
distribution, biotransformation, and excretion of drugs.
o Absorption refers to what happens to a drug from the time it is introduced to the body until
it reaches the circulating fluids and tissues.
o Distribution involves the movement of a drug to the body’s tissues.
o Biotransformation (Metabolism) - The liver is the most important site of drug metabolism,
or biotransformation, the process by which drugs are changed into new, less active
chemicals.
o Excretion is the removal of a drug from the body. The skin, saliva, lungs, bile, and feces are
some of the routes used to excrete drugs.
 The goal of established dosing schedules is to achieve a critical concentration of the drug in the body.
This critical concentration is the amount of the drug necessary to achieve the drug’s therapeutic
effects.
 Arriving at a critical concentration involves a dynamic equilibrium among the processes of drug
absorption, distribution, metabolism or biotransformation, and excretion.
 Absorption involves moving a drug into the body for circulation. Oral drugs are absorbed from the
small intestine, undergo many changes, and are affected by many things in the process. IV drugs are
injected directly into the circulation and do not need additional absorption.
 Drugs are distributed to various tissues throughout the body depending on their solubility and
ionization. Most drugs are bound to plasma proteins for transport to reactive tissues.
 Drugs are metabolized or biotransformed into less toxic chemicals by various enzyme systems in the
body. The liver is the primary site of drug metabolism or biotransformation. The liver uses the
cytochrome P450 enzyme system to alter the drug and start its biotransformation.
 The first-pass effect is the breakdown of oral drugs in the liver immediately after absorption. Drugs
given by other routes often reach reactive tissues before passing through the liver for
biotransformation.
 Drug excretion is removal of the drug from the body. This occurs mainly through the kidneys.
 The half-life of a drug is the period of time it takes for an amount of drug in the body to decrease to
one half of the peak level it previously achieved. The half-life is affected by all aspects of
pharmacokinetics. Knowing the half-life of a drug helps in predicting dosing schedules and duration
of effects.
 The actual effects of a drug are determined by its pharmacokinetics, its pharmacodynamics, and
many human factors that can change the drug’s effectiveness.
 To provide the safest and most effective drug therapy, the nurse must consider all of the possible
factors that influence drug concentration and effectiveness.
3. Toxic Effects of Drugs
 Adverse effects - are undesired effects that may be unpleasant or even dangerous. They can occur
for many reasons, including the following:
o The drug may have other effects on the body besides the therapeutic effect.
o The patient may be sensitive to the drug being given.
o The drug’s action on the body may cause other responses that are undesirable or
unpleasant.
o The patient may be taking too much or too little of the drug, leading to adverse effects.
 Adverse drug effects can range from allergic reactions to tissue and cellular damage. The nurse, as
the health care provider most associated with drug administration, needs to assess each situation
for potential adverse effects and intervene appropriately to minimize those effects.
 Adverse effects can be extensions of the primary action of a drug or secondary effects that are not
necessarily desirable but are unavoidable.
 Allergic reactions can occur when a person’s body makes antibodies to a drug or drug protein. If the

person is exposed to that drug at another time, an immune response may occur. Allergic reactions
can be of various types. The exact response should be noted to avoid future confusion in patient
care.
 Tissue damage can include skin problems, mucous membrane inflammation, blood dyscrasias,
superinfections, liver or renal toxicity, poisoning, hypoglycemia or hyperglycemia, electrolyte
disturbances, various CNS problems (ocular damage, auditory damage, atropine-like effects,
Parkinson-like syndrome, NMS), and teratogenicity.
4. The Nursing Process in Drug Therapy and Patient Safety
 Nursing is a complex art and science that provides for nurturing and care of the sick, as well as
prevention and education services.
 Components of the nursing assessment (history of past illnesses and the current complaint, as well
as a physical examination) provide a database of baseline information to ensure safe administration
of a drug and to evaluate the drug’s effectiveness and adverse effects.
 Nursing assessment must include information on the history of past illnesses and the current
complaint, as well as a physical examination; this provides a database of baseline information to
ensure safe administration of a drug and to evaluate the drug’s effectiveness and adverse effects.
 Nursing diagnoses are developed from the information gathered during the assessment phase of the
nursing process. A nursing diagnosis states the actual or potential response of a patient to a clinical
situation.
 Implementation involves taking the information gathered and synthesized into nursing diagnoses to
plan the patient care. This process includes determining the desired patient outcomes, setting goals
for safe and effective drug administration, providing comfort measures to help the patient cope with
the therapeutic or adverse effects of a drug, and providing patient and family education to ensure
safe and effective drug therapy.
 Evaluation is part of the continuing process of patient care that leads to changes in assessment,
diagnosis, and intervention. The patient is continually evaluated for therapeutic response, the
occurrence of adverse drug effects, and the occurrence of drug–drug, drug– food, drug–alternative
therapy, or drug–laboratory test interactions.
 A nursing care guide and patient education materials can be prepared for each drug being given,
using information about a drug’s therapeutic effects, adverse effects, and special considerations.
Prevention of medication errors is a complicated task that involves the prescriber, the pharmacist, the
nurse administering the drugs, and the patient. The nurse needs to be vigilant in administering drugs
to check the seven “rights” of drug administration. The patient needs to be educated to be his or her
own advocate and to take steps to avoid medication errors
Comfort Measures - Nurses are in a unique position to help the patient cope with the effects of drug
therapy.
Placebo Effect - The anticipation that a drug will be helpful (placebo effect) has proved to have
tremendous impact on the actual success of drug therapy.
Managing Adverse Effects - Interventions can be directed at promoting patient safety and
decreasing the impact of the anticipated adverse effects of a drug. Such interventions
include environmental control (e.g., temperature, light), safety measures (e.g., avoiding
driving, avoiding the sun, using side rails), and physical comfort measures (e.g., skin care,
laxatives, frequent meals).
o Lifestyle Adjustment - Some medications and their effects require that a patient make
changes in his or her lifestyle. For example, patients taking diuretics may have to rearrange
their day so as to be near toilet facilities when the drug action peaks.

6. Dosage Calculations
 Measuring Systems - at least four different systems are currently used in drug preparation and
delivery: the metric system, the apothecary system, the household system, and the avoirdupois
system.
o The metric system is the most widely used system of measure. It is based on the decimal

system, so all units are determined as multiples of 10.

o The apothecary system is a very old system of measurement that was specifically

developed for use by apothecaries or pharmacists. The apothecary system uses the minim
as the basic unit of liquid measure and the grain as the basic unit of solid measure
o The household system is the measuring system that is found in recipe books. This system
uses the teaspoon as the basic unit of fluid measure and the pound as the basic unit of

solid measure.
o The avoirdupois system is another older system that was very popular when pharmacists
routinely had to compound medications. This system uses ounces and grains, but they
measure differently than those of the apothecary and household systems.
 Conversion Between Systems - simplest way to convert measurements from one system to another
is to set up a ratio and proportion equation. The ratio containing two known equivalent amounts is
placed on one side of an equation, and the ratio containing the amount you wish to convert and its
unknown equivalent is placed on the other side.
 Calculating Dose - because there are several systems of measurement available that might be used
when a drug is ordered and because drugs are made available only in certain forms or doses, it may
be necessary to calculate what the patient should be receiving.
o Oral Drugs
o Parenteral Drugs
o Intravenous Solutions
o Pediatric Considerations
Reference:
Karch, A. M. (2013). Focus on nursing pharmacology. Sixth edition. Philadelphia: Wolters Kluwer.