Pharmacodynamics Flashcards
7 cards from real Pharmacology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Pharmacodynamics flashcards as text
The concept of 'biased agonism' (functional selectivity) refers to a drug that:
Answer: Preferentially activates one signaling pathway over another at the same receptor
Biased agonists stabilize distinct receptor conformations that preferentially couple to one downstream pathway (e.g., G-protein vs. arrestin), allowing selective therapeutic effects.
The safety margin of a drug is BEST improved by:
Answer: Increasing the LD50 relative to the ED50 (higher therapeutic index)
A higher therapeutic index (LD50/ED50) means a larger separation between the lethal and effective doses, providing a greater margin of safety in clinical use.
Which pharmacodynamic mechanism explains why benzodiazepines enhance GABA's effect without activating GABA-A receptors alone?
Answer: Allosteric positive modulation that increases frequency of chloride channel opening
Benzodiazepines bind an allosteric site on GABA-A receptors, increasing the frequency of chloride channel opening in response to GABA without directly gating the channel.
A competitive antagonist, when present, will cause which change to the agonist's dose-response curve?
Answer: Rightward shift in EC50 with Emax preserved (if overcome by excess agonist)
Competitive antagonists reversibly occupy the receptor and shift the agonist dose-response curve to the right (higher EC50) but the original Emax can be restored by adding more agonist.
Nuclear receptors differ from membrane receptors in that they:
Answer: Directly regulate gene transcription, producing effects over hours to days
Nuclear receptors (e.g., for glucocorticoids, thyroid hormones, estrogen) act as ligand-activated transcription factors, directly modifying gene expression with a delayed but prolonged effect.
Drug tolerance that results from increased metabolic breakdown of a drug over time is classified as:
Answer: Pharmacokinetic tolerance
Pharmacokinetic (dispositional) tolerance occurs when repeated drug exposure induces enzymes (e.g., CYP450) that accelerate drug metabolism, reducing plasma concentrations and effect.
The concept of 'volume of distribution' (Vd) is a pharmacokinetic parameter, but a very high Vd affects pharmacodynamics by:
Answer: Reducing the plasma concentration available to act at central receptors
A high Vd indicates extensive distribution into peripheral tissues, lowering plasma concentrations and thus the amount of drug reaching receptors in plasma-accessible compartments.