Autonomic Pharmacology USMLE Step 1 Practice Question
A 29-year-old man with generalized anxiety disorder started on propranolol 80 mg daily presents with improved palpitations and tremor. However, he continues experiencing excessive diaphoresis and sense of impending doom. Vital signs show BP 118/76 mmHg, HR 68 bpm, RR 16/min, temperature 37°C. Recent labs reveal normal TSH and cortisol levels. He denies polyuria or polydipsia. Which mechanism best explains why propranolol failed to relieve his anxiety and diaphoresis?
Answer choices
- APropranolol blocks muscarinic receptors preventing parasympathetic compensation
- BPropranolol blocks only β-adrenergic peripheral manifestations, not central anxiety mediated by neurotransmittersCorrect answer
- CPropranolol increases GABA reuptake, worsening anxiety
- DPropranolol inhibits α1-adrenergic receptors causing reflex tachycardia
- EPropranolol enhances serotonin metabolism in the amygdala
- FPropranolol causes downregulation of benzodiazepine receptors in the limbic system
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