Adverse drug reactions
Practice questions with explanations

B. Trials involve limited numbers, selected patients and short durations, so rare, delayed or population-specific reactions appear only with widespread use

A trial of a few thousand patients cannot detect a reaction occurring in one in ten thousand, and trials exclude the pregnant, the very old, the multimorbid and those on many other drugs, who then take the drug in practice. Delayed effects and interactions also emerge only with time, which is why post-marketing surveillance is not an optional extra.

D. A rise in transaminases or bilirubin with a plausible temporal relationship to a new drug, improving after cessation

Drug-induced liver injury is a diagnosis of exclusion supported by timing, the known profile of the drug and improvement on withdrawal. Patterns differ: flucloxacillin and co-amoxiclav cause cholestatic injury often after the course finishes, paracetamol causes hepatocellular necrosis, and herbal and complementary products are a frequently overlooked cause.

D. Cardiovascular drugs, antithrombotics, diuretics and analgesics including NSAIDs and opioids

Bleeding on antithrombotics, electrolyte disturbance and falls with diuretics and antihypertensives, hypoglycaemia with insulin and sulfonylureas, and gastrointestinal and renal harm from NSAIDs account for a large share of medicine-related admissions, and a substantial proportion are judged preventable. That is the case for structured review and monitoring.