Lab 3 2
nd
class
Pharmacology: Science that is concern with the study of the interaction of the drug with living
system as regard:
- Pharmacodynamic (biological effect and mechanism of action on different body organ): The
effect of drug on the body.
-Pharmacokinetics (absorption, distribution, metabolism and excretion): The effect of the body
on the drug.
- Pharmacotherapeutics (uses in treatment of diseases in specific dosage forms and interactions
with other drugs).
- Pharmacogenetics: The study of how a person's genes affect the way responds to drugs.
Drugs: The substance either obtain naturally since (plant, animal) or synthesize and this
substance have ability to influence the physiological or biochemical activity of cell.
Receptor: Is specialized target macromolecule present in cell surface or intracellular, that binds
a drug and produce pharmacological action.
Properties of receptors:
1- protein in structure. 2- selectivity.
3- sensitivity. 4- specificity.
Ligand: drug or endogenous substance that binds to a receptor.
Affinity: ability of a ligand to combine with its receptor.
Potency: a measure of the amount of a ligand required to produce a given level of effect.
Efficacy: ability of a ligand to provoke a cellular response after combining with its receptor and
depend on number of drug receptor complex formed.
Drugs are classified into agonist, antagonist, partial agonist and inverse agonists according
to action on cell receptors:
Agonist: a ligand that produced an appropriate response when it binds its receptor have affinity
and efficacy.
Partial agonist: agonist that cannot elicit the same maximum response as a full agonist e.g. have
affinity but with low efficacy.
Inverse agonist: a ligand that produce effect which are specifically opposite to those of agonist
and affinity for specific receptor.
Antagonist: Are drug that decrease or oppose the action of another drug, antagonist has no
effect if an agonist is not present, a ligand which binds to receptor but do no initiate cellular
response e.g. have affinity but not efficacy for their cognate receptor.
Synergism is of two sort:
1- Additive: Total pharmacological of combination of two drug or more summation individual
pharmacological action.
2- Potentiation: One drug increase the action of another.
Desenitisation and tachyphylaxis: The effect of drug rapidly diminishes when it is given
continuously or repeatedly.
Tolerance: A more gradual decrease in responsiveness to a drug, taking days or weeks to
developed.
Drug resistance: Loss of effectiveness of antimicrobial or antitumor drug.
Prophylactic drugs: drugs that prevent or decrease the severity of a disease.
A legend drug: A drug sold only by prescription and labeled.
An over-the-counter: A drug may be sold without a prescription.