Interaction between posaconazole and flucloxacillin in a lung transplant patient: decrease in plasma exposure of posaconazole and possible undertreatment of invasive aspergillosis: case report.

We describe a new interaction between posaconazole and flucloxacillin. Presumably the underlying mechanism is activation of the pregnane X receptor by flucloxacillin, which can induce cytochrome P450, uridine glucuronosyl transferase (UGT1A4) and P-glycoprotein. We advise caution when combining flucloxacillin and triazoles, because interactions may lead to undertreatment of invasive aspergillosis.