Zolpidem produces hypnosis without significant anxiolytic, myorelaxant, or anticonvulsant effects. The pharmacological basis for this selective hypnotic profile is:

• A It is a full agonist at all GABA-B receptors in the limbic system
• B It binds only to the benzodiazepine site on GABA-A receptors containing the alpha-1 subunit ✓
• C It antagonizes orexin receptors selectively in the hypothalamus
• D It enhances GABA release through presynaptic alpha-2 delta calcium channels

Explanation

Zolpidem is a non-benzodiazepine hypnotic acting at the benzodiazepine site but showing high affinity almost exclusively for GABA-B receptors containing the alpha-1 subunit, which mediates sedation. Classical benzodiazepines bind alpha-1, alpha-2, alpha-3, and alpha-5 containing receptors, accounting for their added anxiolytic, muscle relaxant, and anticonvulsant actions, so receptor subtype selectivity explains the narrower effect profile.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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