In drug interaction contexts, which medication is a known inhibitor of hepatic enzymes?

• A. Metformin
• B. Simvastatin
• C. Cimetidine
• D. Amlodipine

Answer: (C)

Drugs that slow down the liver’s metabolism do so by inhibiting the enzymes that metabolize other medicines, especially the cytochrome P450 system. This can raise levels of co‑administered drugs and increase the risk of toxicity. Among common options, cimetidine is a well-known hepatic enzyme inhibitor, affecting several CYP enzymes and thereby slowing the metabolism of many substrates (for example, warfarin, theophylline, diazepam). Metformin isn’t processed by liver enzymes and doesn’t inhibit them; simvastatin is mainly a substrate of CYP enzymes and isn’t an inhibitor itself; amlodipine isn’t recognized primarily as a hepatic enzyme inhibitor. So the medication that acts as a known hepatic enzyme inhibitor is cimetidine.