A resident suggests buspirone for a patient with generalised anxiety disorder. The patient asks whether he may take a tablet only on days he feels anxious, as he did with his previous medication. Why is buspirone unsuitable for as-needed use?

• A It requires plasma concentration above 100 ng/mL for effect
• B Its anxiolytic effect appears only after 1 to 2 weeks of continuous dosing ✓
• C It causes immediate tolerance requiring escalation of dose
• D It is a positive allosteric modulator needing steady-state levels

Explanation

Buspirone is a 5-HT1A receptor partial agonist whose anxiolytic effect emerges only after 1 to 2 weeks of regular administration, so it cannot abort acute anxiety the way benzodiazepines do. Its advantages are absence of sedation, dependence, tolerance, and interaction with alcohol, making it suitable for chronic generalised anxiety. Option A cites a toxic threshold rather than a therapeutic one, and option D describes benzodiazepines, which act at GABA-A receptors.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

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