Does Phenytoin Interact With Verapamil?

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine a The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable 7.3 Drug/Laboratory Test …

Severity: Moderate

Severity basis: drug interactions section (keywords: may increase). Combining Phenytoin (Anticonvulsant) and Verapamil (Calcium channel blocker) is classified as a moderate interaction.

What to Do

Use this combination with caution. Your prescriber may monitor you more closely or adjust doses.

From the FDA Label

Phenytoin when given with the combination of fosamprenavir and ritonavir may increase the concentration of amprenavir Calcium channel blockers Nifedipine, nimodipine, nisoldipine, verapamil Other Albendazole (decreases active metabolite), chlorpropamide, clozapine, cyclosporine, digoxin, disopyramide, folic acid, methadone, mexiletine, praziquantel, quetiapine a The effect of phenytoin on phenobarbital, valproic acid and sodium valproate serum levels is unpredictable 7.3 Drug/Laboratory Test …

Source: FDA structured product labeling (set_id 035a8d4e-2063-4240-83cb-d7eebcabe301).

Phenytoin

Anticonvulsant

Brands: Dilantin

View Phenytoin safety profile

Verapamil

Calcium channel blocker

Brands: Calan, Verelan

View Verapamil safety profile

Check these against your full medication list in our free Interaction Checker

This information is educational — not medical advice.

This page is provided for general educational purposes and summarizes publicly available data from sources such as the U.S. Food & Drug Administration. It is not a substitute for the judgment of a licensed clinician and should not be used to start, stop, or change any medication. It may be incomplete or out of date, and individual circumstances vary. Always talk with your prescriber or pharmacist about your specific medications and health conditions. If you think you may have a medical emergency, call 911.

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