Interaction between flucloxacillin and azoles: Is isavuconazole next?

Area of Science:

• Pharmacology
• Infectious Diseases
• Drug Interactions

Background:

• Isavuconazole is a triazole antifungal used for invasive aspergillosis and mucormycosis.
• Flucloxacillin may reduce voriconazole levels; a similar interaction with isavuconazole is possible due to shared metabolism via cytochrome P450 enzymes.

Purpose of the Study:

• To document isavuconazole exposure in patients receiving concomitant flucloxacillin treatment.

Main Methods:

• Case series reporting on two patients treated with both isavuconazole and flucloxacillin.
• Determination of isavuconazole concentrations in these patients.

Main Results:

• Two patients receiving concomitant flucloxacillin showed low isavuconazole trough concentrations (<1 mg/L).

Conclusions:

• Concomitant flucloxacillin use can lead to low isavuconazole concentrations.
• Dose augmentation may achieve adequate exposure, and therapeutic drug monitoring is advised.