Drug-Drug Interaction


SELECTED ANTICONVULSANTS/MARAVIROC

MECHANISM OF ACTION
Carbamazepine, phenobarbital, and phenytoin may induce the metabolism of maraviroc by CYP P-450-3A4.(1)

DISCUSSION
In a study in 12 subjects, concurrent rifampin (600 mg daily, another inducer of CYP P-450-3A4) decreased the minimum concentration (Cmin), area-under-curve (AUC), and maximum concentration (Cmax) of maraviroc (100 mg twice daily) by 78%, 63.2%, and 66.3%, respectively.(1)

CLINICAL EFFECTS
Concurrent use of carbamazepine, phenobarbital, or phenytoin in the absence of an inhibitor of CYP P-450-3A4 and without a dosage adjustment of maraviroc may result in decreased levels and effectiveness of maraviroc.(1)

SEVERITY LEVEL
2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

PATIENT MANAGEMENT
The US manufacturer of maraviroc states that patients receiving therapy with inducers of CYP P-450-3A4, such as carbamazepine, phenobarbital, or phenytoin who are not also receiving an inhibitor of CYP P-450-3A4 should receive a dose of 600 mg maraviroc twice daily.(1)

PREDISPOSING FACTORS
This interaction may be more severe in patients with renal impairment.(1)

REFERENCE

  1. Selzentry (maraviroc) US prescribing information. Pfizer Inc. May, 2010. .Selzentry (maraviroc) US prescribing information. Pfizer Inc. May, 2010.