On your way to an examination, you experience the vulnerable feeling that an attack of diarrhea is imminent. Which one of the following anti-diarrheal drugs could you buy without a prescription even though it is related chemically to the strong opioid-analgesic meperidine?

Correct Answer: C

Rationale: Loperamide, available OTC, is structurally related to meperidine and acts as an opioid agonist to reduce diarrhea.

Correct Answer: C

Rationale: Metoclopramide is a prokinetic agent that enhances gastric emptying, making it suitable for emergency preoperative use to reduce aspiration risk.

Correct Answer: D

Rationale: Ondansetron is a 5-HT3 antagonist primarily used as an antiemetic, especially in cancer chemotherapy-induced nausea and vomiting.

Correct Answer: C

Rationale: The WHO ORS formulation contains 90 mmol/L of sodium, balanced for effective rehydration in diarrhea.

Correct Answer: C

Rationale: Scopolamine (hyoscine) is the most potent antimotion sickness drug due to its strong anticholinergic effects on the vestibular system.