Drug Interaction Report

Coadministration with modafinil (the racemate) or armodafinil (the R-enantiomer) may decrease the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. Modafinil and armodafinil are modest inducers of CYP450 3A4, and pharmacokinetic studies suggest that their effects may be primarily intestinal rather than hepatic. Thus, clinically significant interactions would most likely be expected with drugs that have low oral bioavailability due to significant intestinal CYP450 3A4-mediated first-pass metabolism (e.g., buspirone, cyclosporine, lovastatin, midazolam, saquinavir, simvastatin, sirolimus, tacrolimus, triazolam, calcium channel blockers). However, the potential for interaction should be considered with any drug metabolized by CYP450 3A4, especially given the high degree of interpatient variability with respect to CYP450-mediated metabolism. Pharmacologic response to these drugs may be altered and should be monitored more closely whenever modafinil or armodafinil is added to or withdrawn from therapy. Dosage adjustments may be required if an interaction is suspected.

GENERALLY AVOID: Acute ethanol ingestion may potentiate the CNS effects of many benzodiazepines. Tolerance may develop with chronic ethanol use. The mechanism may be decreased clearance of the benzodiazepines because of CYP450 hepatic enzyme inhibition. Also, it has been suggested that the cognitive deficits induced by benzodiazepines may be increased in patients who chronically consume large amounts of alcohol.

MANAGEMENT: Patients should be advised to avoid alcohol during benzodiazepine therapy.

Administration with food may delay the absorption of modafinil (the racemate) and armodafinil (the R-enantiomer) without significantly affecting their overall bioavailability. According to the product labeling, modafinil's absorption may be delayed by approximately one hour if taken with food. Similarly, the time to reach peak plasma concentration (Tmax) of armodafinil may be delayed by approximately 2 to 4 hours in the fed state.