A 30-year-old man with generalized anxiety disorder is started on buspirone. He returns after 3 days complaining that the drug 'is doing nothing.' Which statement about buspirone best explains this encounter?
- A It is a benzodiazepine receptor antagonist and needs dose escalation
- B It is a partial agonist at 5-HT1A receptors and requires 2 to 4 weeks for anxiolytic effect ✓
- C It acts within hours but only at doses above 60 mg/day
- D It is a full agonist at GABA-A receptors and tolerance develops rapidly
Correct answer: B. It is a partial agonist at 5-HT1A receptors and requires 2 to 4 weeks for anxiolytic effect
Explanation
Buspirone is a partial agonist at presynaptic and postsynaptic 5-HT1A receptors. Like antidepressants, its anxiolytic effect takes 2 to 4 weeks to appear, so early non-response is expected and is not an indication to abandon the drug. It has no affinity for GABA-A or benzodiazepine receptors, which kills options A and D, and it carries no risk of dependence or sedation. This delayed onset is the single most examined fact about buspirone.
Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.
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