MECHANISM OF ACTION
Concurrent use of carbamazepine, phenobarbital,
phenytoin, or primidone may induce the metabolism of nifedipine(1) and
nimodipine.(2,3)
DISCUSSION
Coadministration of phenytoin with nifedipine (10 mg capsule
and 60 mg extended-release tablet) decreased the area-under-curve (AUC) and
maximum concentration (Cmax) of nifedipine by 70%.(1)
CLINICAL EFFECTS
Concurrent use of carbamazepine, phenobarbital,
phenytoin, or primidone may result in decreased levels and effectiveness of
nifedipine(1) or nimodipine.(2,3)
SEVERITY LEVEL
1-Contraindicated Drug Combination: This drug combination
is contraindicated and generally should not be dispensed or administered to
the same patient.
PATIENT MANAGEMENT
The US manufacturer of nifedipine states that the
concurrent use of strong CYP P-450-3A4 inducers such as carbamazepine,
phenobarbital, or phenytoin is contraindicated.(1)
PREDISPOSING FACTORS
None determined.
REFERENCES