Indicate an irreversible inhibitor of GABA aminotransferase (GABA-T):

Correct Answer: C

Rationale: The correct answer is C: Vigabatrin. Vigabatrin irreversibly inhibits GABA-T by irreversibly binding to its active site, leading to a sustained increase in GABA levels. This results in enhanced GABAergic neurotransmission. Diazepam (A) and Phenobarbital (B) are not inhibitors of GABA-T. Felbamate (D) acts by blocking NMDA receptors and enhancing GABAergic transmission, but it does not directly inhibit GABA-T.

Correct Answer: B

Rationale: The correct answer is B: Disulfiram. Disulfiram inhibits the enzyme aldehyde dehydrogenase, leading to accumulation of acetaldehyde when alcohol is consumed. This causes a noxious reaction (e.g., nausea, vomiting) as acetaldehyde builds up. Naltrexone (A) is an alcohol antagonist that reduces alcohol cravings. Diazepam (C) is a benzodiazepine used for anxiety and alcohol withdrawal symptoms. Morphine (D) is an opioid analgesic and not used for causing a noxious reaction to alcohol.

Correct Answer: B

Rationale: The correct answer is B: Chlorpromazine. Chlorpromazine has significant peripheral alpha-adrenergic blocking activity, leading to side effects like orthostatic hypotension. This is due to its antagonistic action on alpha-1 adrenergic receptors in the peripheral nervous system. Haloperidol (A) primarily acts on dopamine receptors in the brain. Clozapine (C) is known for its anticholinergic effects and does not have significant alpha-adrenergic blocking activity. Risperidone (D) primarily acts on dopamine and serotonin receptors, with minimal alpha-adrenergic blocking activity.

Correct Answer: C

Rationale: The correct answer is C: Fluoxetine. Fluoxetine is a phenyltolylpropylamine derivative due to its chemical structure. It falls under the class of selective serotonin reuptake inhibitors (SSRIs), making it an antidepressant agent. Paroxetine (A) is an SSRI but not a phenyltolylpropylamine derivative. Maprotiline (B) is a tetracyclic antidepressant, not a phenyltolylpropylamine derivative. Amitriptyline (D) is a tricyclic antidepressant, not a phenyltolylpropylamine derivative. Therefore, the correct answer is C.

Correct Answer: D

Rationale: The correct answer is D: Prazepam. Prazepam is preferred for elderly patients due to its long half-life, which reduces the risk of accumulation and potential side effects. Clorazepate (A) and Clordiazepoxide (B) have active metabolites that may accumulate in the elderly. Triazolam (C) has a short half-life, leading to potential next-day sedation. Therefore, Prazepam is the safest choice for elderly patients.