Drug Targets, Selective Toxicity, Therapeutic Index

Question 1

What are the three classes of drugs?

Answer 1

1. Therapeutic use (e.g. antihypertensive, antiepileptic)
2. Molecular mechanism of action (e.g. beta-blocker, monoamine oxidase inhibitor, Ca2+ channel inhibitor)
3. Chemistry (e.g. benzodiazepine, catecholamine)

Question 2

What are the five types of macromolecular drug targets?

Answer 2

a) Hormone/neurotransmitter receptors
b) Enzymes
c) Transporters
d) Ion channels
e) DNA

Question 3

Give an example for each of the macromolecular drug targets, written as receptor/substrate

Answer 3

NT receptors - nAChR / ACh

Enzymes - angiotensin converting enzyme / cholinesterase

Transporters - Na+/K+ pump / cardiac glycosides

Ion channels - Na+ channels / local anaesthetics, e.g. procaine

DNA - effects of some anticancer drugs

Question 4

Define the therapeutic index.

Answer 4

Therapeutic index = maximum non-toxic dose / minimum effective dose

Therapeutic index = TD50 (toxic dose) / ED50 (effective dose)

Therapeutic index = LD50 (lethal dose) / ED50 (effective dose)

Question 5

What two laws are crucial to the study of pharmacology?

Answer 5

Popper’s Law: statements can never be shown to be true - only falsifiable

Carson’s consolation: no experiment is ever useless - it can always be used as a bad example