Clarithromycin is preferred over azithromycin in some Helicobacter pylori regimens but carries a clinically important interaction profile. The basis of clarithromycin's major drug interactions is:
- A Potent induction of intestinal P-glycoprotein reducing absorption of co-administered drugs
- B Displacement of warfarin from albumin binding sites
- C Strong inhibition of CYP3A4 raising levels of substrates such as statins and ergot alkaloids ✓
- D Competitive inhibition of renal tubular organic cation secretion
Correct answer: C. Strong inhibition of CYP3A4 raising levels of substrates such as statins and ergot alkaloids
Explanation
Clarithromycin is a strong CYP3A4 inhibitor, so it elevates levels of simvastatin and atorvastatin, ergotamine, cisapride and carbamazepine, sometimes with serious toxicity including rhabdomyolysis and QT prolongation. Erythromycin shares this property while azithromycin inhibits CYP enzymes minimally, a key differentiator among macrolides. P-glycoprotein interaction exists but is inhibition rather than induction.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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