Pharmacodynamic Mechanisms 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 Pharmacodynamic Mechanisms flashcards as text
Which second messenger is produced when Gs-coupled receptors activate adenylyl cyclase?
Answer: Cyclic AMP (cAMP)
Gs stimulates adenylyl cyclase to convert ATP to cAMP, which then activates protein kinase A (PKA) to phosphorylate intracellular targets.
Noncompetitive (insurmountable) antagonism is characterized by:
Answer: Reduction of Emax that cannot be overcome by increasing agonist dose
Noncompetitive antagonists reduce the maximum effect because they either bind irreversibly or at an allosteric site, precluding full receptor activation regardless of agonist concentration.
Which ion channel mechanism is responsible for the pharmacodynamic action of benzodiazepines?
Answer: Enhancement of GABA-A chloride channel opening frequency
Benzodiazepines act as positive allosteric modulators at GABA-A receptors, increasing the frequency of chloride channel opening in response to GABA.
Drug A has an EC50 of 2 mg/kg and Drug B has an EC50 of 20 mg/kg for the same endpoint. Which statement is correct?
Answer: Drug A is more potent than Drug B
A lower EC50 means a smaller dose produces 50% of the maximum effect, making Drug A more potent than Drug B.
Receptor tyrosine kinase (RTK) signaling is most closely associated with:
Answer: Activation of intracellular kinase cascades (minutes)
RTK activation leads to receptor autophosphorylation and activation of downstream kinase cascades (e.g., MAPK/ERK, PI3K/Akt) within minutes.
The phenomenon of homologous desensitization of GPCRs specifically involves:
Answer: Phosphorylation by GRKs and beta-arrestin recruitment to the agonist-occupied receptor
Homologous desensitization is agonist-specific: GRKs phosphorylate only the occupied receptor, and beta-arrestin binding sterically prevents further G-protein coupling.
Which pharmacodynamic interaction occurs when two drugs together produce an effect less than additive?
Answer: Antagonism
When the combined effect of two drugs is less than the sum of individual effects, the interaction is antagonistic.