Mechanisms of Drug Actions

Question 1

Receptors

Answer 1

Determine the relationship b/t dose/concentration of drug & pharmacologic effects
Are responsible for selectivity of drug action
Mediate the actions of pharmacologic agonists & antagonists

Question 2

Agonist

Answer 2

agent that binds to physiologic receptors & mimic the effects of endogenous regulatory compounds

Question 3

Antagonist

Answer 3

blocks effects of endogenous agonists by competing for the agonist receptor binding site

Question 4

Enzyme inhibiton

Answer 4

drugs may bind to enzymes & modulate their functions

Ex. HMG CoA reductase can be inhibited to lower cholesterol synthesis

Question 5

Intracellular Receptors of Lipid-Soluble Agents

Answer 5

Lipid soluble ligands cross the PM & bind intracellular receptors (steroids & thyroid hormone)

Question 6

Ligand Regulated Transmembrane Enzymes (including RTKs)

Answer 6

Ligand binds extracellular domain causing dimerization & activation of tyrosine kinases & autophosphorylation (insulin)

Question 7

Cytokine Receptors

Answer 7

Ligand binds extracellular domain & activates extrinsic tyrosine domains (JAK) that bind the receptor (GH, EPO & interferon)

Question 8

Ligand & Voltage gated Channels

Answer 8

Nt binds extracellular domain/change in membrane potential across the cell causes opening of ion channel (ACh, serotonin, GABA & glutamate)

Question 9

G proteins & second messengers

Answer 9

Ligand binding Griggs activation of an intercellular G protein & changes activity of an effector element that changes the concentration of a chemical second messenger in the cell (cAMP, Ca ions or phosphoinositides)