Pharmacodynamics and Mechanism of Action Flashcards

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

Answer: The 2 nM drug is more potent

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

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

Answer: Type I (ionotropic)

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

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

Answer: Positive allosteric modulator

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

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

Answer: Down-regulation

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

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

Answer: Competitive antagonism

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

A drug produces a maximal response of only 60% compared to a full agonist at the same receptor. This drug is best described as:

Answer: A partial agonist

A partial agonist produces a submaximal response (less than 100% efficacy) even when all receptors are occupied.

Which second messenger is directly produced by adenylyl cyclase activation following Gs protein stimulation?

Answer: Cyclic AMP (cAMP)

Gs protein activation stimulates adenylyl cyclase to convert ATP into cyclic AMP (cAMP), the primary second messenger in this pathway.