Pharmacology Pharmacodynamic Mechanisms 3

Question 1

The therapeutic index (TI) is calculated as:

Accepted Answer

LD50 / ED50

Answer

ED50 / LD50

Answer

Emax / EC50

Answer

EC50 / Emax

Question 2

Allosteric modulators differ from orthosteric ligands because they:

Accepted Answer

Bind at a site distinct from the endogenous ligand binding site

Answer

Always activate the receptor maximally

Answer

Competitively block endogenous agonist access

Answer

Only function when the receptor is in the inactive state

Question 3

Which mechanism best explains the action of aspirin as an irreversible inhibitor of cyclooxygenase?

Accepted Answer

Covalent acetylation of a serine residue

Answer

Competitive active-site blockade

Answer

Allosteric distortion of the enzyme

Answer

Chelation of a cofactor metal ion

Question 4

A patient's response to a drug increases rather than decreases with repeated administration. This is best described as:

Accepted Answer

Sensitization (reverse tolerance)

Answer

Tolerance

Answer

Tachyphylaxis

Answer

Desensitization

Question 5

Which receptor family primarily signals through G-protein–mediated second messenger cascades?

Accepted Answer

G-protein–coupled receptors (GPCRs)

Answer

Ligand-gated ion channels

Answer

Receptor tyrosine kinases

Answer

Nuclear hormone receptors

Question 6

The concept of 'biased agonism' (functional selectivity) refers to:

Accepted Answer

A single ligand preferentially activating one downstream pathway over another at the same receptor

Answer

Different drugs acting on different receptor subtypes

Answer

Tissue-specific drug metabolism altering effective concentration

Answer

A drug selectively blocking only one receptor subtype

Question 7

The Hill coefficient (n) greater than 1 in a dose-response curve indicates:

Accepted Answer

Positive cooperativity or multiple binding sites

Answer

Inverse agonism at high concentrations

Answer

Negative cooperativity among binding sites

Answer

Reduced drug bioavailability