Persistence of a Posaconazole‐Mediated Drug‐Drug Interaction With Ranolazine After Cessation of Posaconazole Administration: Impact of Obesity and Implications for Patient Safety

The antianginal agent ranolazine (Ranexa®) is metabolized primarily by cytochrome P450‐3A (CYP3A) enzymes. Coadministration with strong CYP3A inhibitors, such as ketoconazole and posaconazole, is contraindicated due to risk of QT prolongation from high levels of ranolazine. This study evaluated the time course of recovery from the posaconazole drug interaction in normal‐weight and otherwise healthy obese subjects. Subjects received single doses of ranolazine in the baseline control condition, again during coadministration of posaconazole, and at 4 additional time points during the 2 weeks after posaconazole discontinuation. With posaconazole coadministration, the geometric mean ratio of ranolazine area under the concentration curve (AUC) increased by a factor of 3.9 in normals and by 2.8 in obese subjects. Posttreatment washout of posaconazole was slow in normals (mean half‐life 36 hours) and further prolonged in obese subjects (64 hours). Recovery of ranolazine AUC toward baseline was delayed. AUC remained significantly elevated above baseline in normal‐weight and obese subjects for 7‐14 days after stopping posaconazole. Current product labeling does not address the need for delay or a reduced dose of ranolazine after discontinuation of a strong CYP3A inhibitor before ranolazine can be safely administered. We recommend that administration of ranolazine should be limited to 500 mg twice daily for 7 days after posaconazole discontinuation in patients with body mass index 18.5‐24.9 kg/m2and for 12 days in patients with body mass index ≥35 kg/m2after ranolazine is resumed.