A 21-year-old woman presents to her primary care physician complaining of “feeling sleepy all the time.” Physical exam is normal, but she has a history of hay fever since she was 14 years old. You discover that she is currently taking medicine for her allergy but cannot remember the name. She says it controls her hay fever symptoms well. You suspect that her medication is causing her to feel sleepy. Which of the following would be most likely to cause drowsiness?

Correct Answer: C

Rationale: Doxylamine, an antihistamine, is known to cause drowsiness due to its sedative effects on the central nervous system.

Correct Answer: C

Rationale: NMDA receptors are crucial for synaptic plasticity and long-term potentiation.

Correct Answer: C

Rationale: Ethosuximide (choice C) treats absence seizures by reducing T-type calcium currents, ideal for brief consciousness lapses. Alprazolam (choice A), Diazepam (choice B), and Midazolam (choice D), benzodiazepines, aren't first-line for absence. Ethosuximide's specificity is key.

Correct Answer: D

Rationale: Chloral hydrate (choice D) is metabolized to trichloroethanol, which depresses the CNS, inducing sedation. Morphine (choice A) metabolizes to active compounds like morphine-6-glucuronide, not trichloroethanol. Clorazepate (choice B) becomes desmethyldiazepam, a benzodiazepine. Phenobarbitone (choice C) is a barbiturate, not metabolized to trichloroethanol. This identifies Chloral hydrate's metabolic pathway, key for its hypnotic use.

Correct Answer: D

Rationale: Carbamazepine (choice D), an anticonvulsant, treats trigeminal neuralgia by stabilizing sodium channels, reducing nerve firing. Phenylbutazone (choice A), an NSAID, and Morphine (choice B), an opioid, aren't first-line. Atropine (choice C), an anticholinergic, is irrelevant. Carbamazepine is the standard therapy.