Which antibiotic is contraindicated (or used with extreme caution) in a patient taking a calcium channel blocker due to a dangerous drug interaction?

Clarithromycin, a macrolide antibiotic, is a potent inhibitor of cytochrome P450 3A4 (CYP3A4), the enzyme responsible for metabolizing most calcium channel blockers (amlodipine, nifedipine, verapamil, diltiazem). Concurrent use of clarithromycin and calcium channel blockers significantly increases plasma levels of the calcium channel blocker, leading to excessive vasodilation, severe hypotension, and an increased risk of acute kidney injury. Studies have shown a substantially increased risk of hospitalization for hypotension when these drugs are co-prescribed. Azithromycin is the preferred macrolide alternative in patients on calcium channel blockers because it does not inhibit CYP3A4.