The following drug is useful in treatment of Parkinsonism:

Correct Answer: A

Rationale: L-DOPA (choice A) treats Parkinsonism by crossing the blood-brain barrier and converting to dopamine, replenishing deficient levels. a-Methyldopa (choice B) lowers blood pressure, not Parkinsonism. Haloperidol (choice C), a dopamine antagonist, worsens it. Physostigmine (choice D), a cholinesterase inhibitor, aids cognition, not movement. L-DOPA's role is central to Parkinson's management.

Correct Answer: C

Rationale: Alprazolam (choice C), a benzodiazepine, treats panic disorders by enhancing GABA, reducing acute anxiety. Thiopentone (choice A), an anesthetic, and Paraldehyde (choice B), a sedative, aren't for panic. Chlorpromazine (choice D), an antipsychotic, targets psychosis, not panic. Alprazolam's specificity is key.

Correct Answer: B

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: Leflunomide (choice D) manages rheumatoid arthritis by inhibiting pyrimidine synthesis, reducing immune-mediated joint damage. Psoriasis (choice A), peptic ulcer (choice B), and colon cancer (choice C) involve different pathologies (e.g., skin, GI, oncology), not leflunomide's target. This reflects its immunomodulatory role.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.