Summary Unit 1: Principles of drug action

Principle of Pharmacology
taught

Rep 1

Rep 2

Rep 3

Status




Unit 1: Principles of Drug Action
Agonists
definition

affinity
the ability or tendency of an agonist to bind to a receptor to form a complex,
quantified by the affinity constant (KA), represent the likely hood of a Drug-
receptor complex forming
higher the affinity, lower ka



efficacy
the ability of an agonist to produce a biological effect




Principle of Pharmacology 1

, potency
a measure of the concentrations of a drug at which is effective



EC50 (C for concentration)
the effective concentration of an agonist which produce 50% of the maximum
possible response
(conc. at 50% response)



ED50 (D for dose)
the effective dose of an agonist which produce 50% of the maximum possible
response

(dose at 50% response)



full agonist and partial agonist




Principle of Pharmacology 2

, to note: no matter how high conc of partial agonist, cannot produce maximal
activation



inverse agonist

drug produce an effect opposite to that agonist, but compete for same receptor,
have -ve efficacy
e.g. antihistamines to histamine H1 receptor




Principle of Pharmacology 3

, pharmacodynamics

(the action of drug on the body, inhibit or enhance)

the effect a drug has on the body enables an appropriate choice of therapeutic
tool



pharmacokinetics
(the action of the body on drug, ADME)

what the body reacts to a drug enables an appropriate dose rate to be selected,
which varies across species



Know how agonists interact with target molecules and the relationship between
concentration and response;

Explain the following terms: affinity, efficacy, potency, EC50 and ED50, spare
receptor hypothesis;




Principle of Pharmacology 4