Pharmacology Pharmacodynamics and Mechanism of Action 2

Question 1

A drug with an EC50 of 2 nM is compared to one with an EC50 of 20 nM. Which statement is correct?

Accepted Answer

The 2 nM drug is more potent

Answer

A lower EC50 means less drug is needed to achieve half-maximal effect, indicating greater potency.

Question 2

Which receptor mechanism involves a ligand-gated ion channel that opens within milliseconds of agonist binding?

Accepted Answer

Type I (ionotropic)

Answer

Type I (ionotropic) receptors are ligand-gated ion channels that produce rapid responses within milliseconds.

Question 3

A drug that binds to an allosteric site and enhances agonist binding without activating the receptor itself is called a:

Accepted Answer

Positive allosteric modulator

Answer

A positive allosteric modulator potentiates agonist-induced receptor activation by binding to a site distinct from the orthosteric site.

Question 4

Which phenomenon describes the decreased response to a drug after repeated dosing due to receptor internalization?

Accepted Answer

Down-regulation

Answer

Down-regulation refers to the decrease in receptor number or sensitivity following prolonged agonist exposure, often via receptor internalization.

Question 5

The Schild equation is used to characterize which type of drug interaction?

Accepted Answer

Competitive antagonism

Answer

The Schild equation quantifies competitive antagonism by relating the dose ratio to antagonist concentration, yielding the pA2 value.

Pharmacology Practice Test