On your way to take an examination, you suddenly get an attack of diarrhea. If you stop at a drug store for an over-the-counter opioid with antidiarrheal action, you will be asked for

Correct option is D

Ans (d)
Sol. Concept and Explanation:
Diarrhea Management:
Diarrhea is treated by slowing intestinal motility, allowing more time for water and electrolytes to be absorbed in the intestines. This reduces the frequency and urgency of bowel movements.
Why Loperamide?
Action:
Loperamide is a peripheral opioid receptor agonist. It binds to mu-opioid receptors in the gut and slows down intestinal contractions, reducing diarrhea without affecting the central nervous system (CNS).
Safety Profile:
Loperamide does not cross the blood-brain barrier, so it lacks the central effects of opioids like sedation or dependence. This makes it safe for most people, even during activities like attending an examination.
Ease of Use:
It is widely available over-the-counter and provides quick relief from acute diarrhea.
Why Not the Other Options?
Codeine (Option a):
Codeine is a central-acting opioid with systemic effects, including sedation and respiratory depression. It is not commonly used for diarrhea due to its potential for addiction and significant CNS side effects.
Dextromethorphan (Option b):
Dextromethorphan is a cough suppressant that acts on the brain. It is unrelated to diarrhea management and has no role in treating gastrointestinal conditions.
Diphenoxylate (Option c):
Diphenoxylate is another opioid used to treat diarrhea, but it can cross the blood-brain barrier at high doses. It is often combined with atropine to discourage misuse. It requires more caution than loperamide and is less commonly recommended for acute situations.