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INTRODUCTION
Definition of Pharmacology
Pharmacology has been defined in many ways:

Pharmacology is a science that studies drug effects within a living system (McKenry &
Salerno, 1995).

Study of effects of chemical substances on the function of living systems i.e. how
chemicals interact with living organisms to produce biological effects.

Pharmacology deals with all kinds of drugs: legal or illegal, prescription or nonprescription (OTC).
There is great concern for the therapeutically useful effects while minimizing potential
harmful effects. Drug use is a mainstay in care or treatment of clients/ patients. Commonly
used for:
Curative purpose

Suppress, signs and symptoms, hence improve quality of life

Preventive/ prophylaxis

Diagnosis
This has resulted to increased quality of life and extension of lifespan.
Nurses need to develop a rational use of drugs to maximize their benefits and minimize their
harmful effects while being accountable for the use of drug therapy.
Knowledge of the drug (Pharmacology), patient/client and the diseased/altered health state is
vital for the rational use of drug therapy.
The nurse need to understand any medication before giving it to the client: dose, route of
administration, Indication(s), side effects & adverse reactions, toxic effects, major drug
interactions and contraindications. Appropriate nursing assessment, planning, implementation,
evaluation techniques are necessary to safely administer the drug.
Historical background
Pharmacology is a young science dating back to mid 19th century. Primitive people believed that
disease was caused by devil and evil spirits. This explains why sick people were mistreated,
especially those with mental illness. Methods of treatment like blood letting, wiping were used.
Religion was also used to treat disease through rituals like sacrifices. Different people e.g.
Egyptians, Greeks, Chinese had their tradition way of treating illness. In the 5th century,
Hippocrates (460-377BC) (Father of medicine) and Galen (his follower) replaced demoniacal
concepts of disease by a theory and practice of medicine based on observation and natural
causes. He said that the causes of disease need to be investigated so that they can be dealt with
accordingly. They proposed the humoral theory of disease where disease was seen as being
caused by disturbance in the body of the distribution of the four humours-black bile, yellow bile,
blood and phlegm Despite their teachings, the demonical cause of disease continued to rule most
parts of the world. In 16th century, a Swiss physician, Paracelsus denounced humoral pathology
(advanced by Hippocrates and Galen). He thought that disease was caused by specific entities
which could be combated by specific remedies. He introduced mercury to Rx syphilis and
advocated the use of single dose instead of mixtures (usually used that time). Paracelsus is
referred as “Father of pharmacology”
In the 17th, 18th and 19th great progress was made in knowledge of biology, chemistry, which
led to the development of science of pharmacology.
Knowledge in other subjects like biochemistry, microbiology and physiology has contributed to
advancement of pharmacology knowledge. In the 20th pharmacology evolved as a complex
science where purified chemicals have been produced from plants, animals, minerals, microbial
cultures e.g. Sertuner’s discovery of morphine 1815, William Withering – digitalis – 1785. In the
1920s, 30s, 40s there was great development of antibiotics e.g. sulfonamides & penicillin. In the
21st century – more drugs continue to be discovered.
NB: As clients get more informed due to greater accessibility to information, nurses will need to
keep updated to new developments in pharmacology so that he/she shall be more accountable to
the client’s quality of care.
Definition of common terms used in pharmacology
1. Drug
Any substance used in diagnosis, cure, treatment or prevention of a disease or condition.
Terms medication, medicine and medicinal are also used.
2. Action of a Drug
Chemical changes or effects that a drug has on body cells and tissues.
3. Indication
An illness or disorder for the treatment of which a specific drug has a documented usefulness.
3. Contra indication
A condition/state that would preclude the administration of a drug.
4. Excipients
Inert substance that forms a base of a drug e.g. diluents, binders, dissolution enhancers, coatings,
flavorings, colorings.
5. Half-life or Half time (t½)
Time taken for plasma concentration of a drug to fall by half or 50%.
One is able to predict how plasma concentration alters over time. Enables one to maintain a
steady state of a drug for maximum effects and minimum side effects e.g. paracetamol =
2hrs.Half-life is determined by rate of biotransformation and excretion of a drug hence any
disease of the liver and kidney requires the dose to be reduced since t½ is prolonged – leading to
possible toxicity.
6. Pharmacokinetics
The study of the action of drugs within the body; including absorption, distribution, metabolism
(biotransformation) and excretion/elimination.
How the body handles drugs from the site of administration to the site of action and elimination.
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