Diltiazem and Ketoconazole interaction
Diltiazem and Ketoconazole: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Diltiazem (DILTIAZEM HYDROCHLORIDE in SODIUM CHLORIDE) label · effective 2025-04-15
Strong or moderate CYP 3A inhibitors a Examples b : Ketoconazole, itraconazole, cimetidine Patients currently receiving diltiazem therapy should be carefully monitored for a change in pharmacological effect when initiating and discontinuing therapy with strong or moderate inhibitors of CYP3A4.
Effect of other drugs on Diltiazem Cytochrome P450 3A4 Inhibitors/ Inducers Diltiazem is a substrate of the cytochrome P450 3A4 enzyme and inhibitors/inducers may change the pharmacological effect of diltiazem Monitor.
From the Ketoconazole label · effective 2026-07-07
Antiarrhythmics disopyramide, dofetilide, dronedarone, quinidine digoxin Disopyramide, dofetilide, dronedarone, quinidine: The potential increase in plasma concentrations of these drugs when coadministered with ketoconazole may increase the risk of serious cardiovascular events including QT prolongation.
Antivirals indinavir, maraviroc, saquinavir Beta Blockers nadolol Calcium Channel Blockers felodipine, nisoldipine other dihydropyridines, verapamil Calcium channel blockers can have a negative inotropic effect which may be additive to those of ketoconazole.
The potential increase in plasma concentrations of calcium channel blockers when coadministered with ketoconazole tablets may increase the risk of edema and congestive heart failure.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.