Respiratory and gastrointestinal pharmacology
Practice questions with explanations

C. Alginates, which physically prevent reflux of acid into the oesophagus

Alginate combined with an antacid forms a viscous raft that floats on the stomach contents and blocks reflux mechanically, with a fast onset that suits symptomatic relief and pregnancy. Because it works physically rather than by reducing acid, it complements acid suppression, and it is taken after meals and at bedtime rather than before food.

C. Mu receptor activation in the enteric nervous system reduces propulsive motility and increases fluid absorption

Enteric mu receptors slow transit while segmentation continues, and the longer contact time allows more water absorption, producing hard stool. Tolerance does not develop, so prophylactic laxatives are given for the duration. Peripherally acting mu antagonists such as naloxegol block the gut effect without reversing analgesia.

D. It delivers a larger dose over minutes without requiring coordination or a strong inspiratory effort, which a distressed patient cannot produce

A patient too breathless to hold their breath or coordinate an actuation can still breathe tidally through a mask, and oxygen can drive the nebuliser. Evidence shows a metered-dose inhaler with a spacer is equally effective for most exacerbations when technique allows, so the choice is practical rather than pharmacological.