Drug Interactions between fosphenytoin and macimorelin

GENERALLY AVOID: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of macimorelin, which is primarily metabolized by the isoenzyme. Although the interaction has not been evaluated in pharmacokinetic studies, the potential for false positive test results should be considered.

MANAGEMENT: The prescribing information for macimorelin recommends discontinuing potent CYP450 3A4 inducers (e.g., carbamazepine, enzalutamide, lumacaftor, mitotane, phenobarbital, phenytoin, rifamycins, St. John's wort) as well as some moderate ones (e.g., bosentan, efavirenz, etravirine, modafinil) prior to macimorelin administration. A sufficient washout period following discontinuation of the inducers is also advised before using macimorelin. No recommendations are available for other, less potent CYP450 3A4 inducers; however, it may be appropriate to follow the same precaution.