Which of the following antiparkinsonian drugs is an antiviral agent used in the prophylaxis of influenza A2?

Correct Answer: D

Rationale: The correct answer is D: Amantadine. Amantadine is an antiviral agent used in the prophylaxis of influenza A2 by inhibiting the viral replication process. Selegiline (A) is a monoamine oxidase inhibitor used in Parkinson's treatment. Sinemet (B) is a combination of carbidopa and levodopa for Parkinson's symptoms. Pergolide (C) is a dopamine agonist used in Parkinson's disease but has been withdrawn due to side effects. Amantadine is the only antiparkinsonian drug in the list with antiviral properties specifically used for influenza A2.

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.

Correct Answer: C

Rationale: Step-by-step rationale for why Ketamine (choice C) is the correct answer: 1. Ketamine is a known NMDA receptor antagonist, blocking the receptor's activity. 2. By inhibiting NMDA receptors, Ketamine produces dissociative anesthesia. 3. Thiopental (A) is a GABA agonist, Halothane (B) is a volatile anesthetic, and Sevoflurane (D) enhances GABA activity, not acting on NMDA receptors.