Drug Interactions between olutasidenib and sildenafil

GENERALLY AVOID: Coadministration with grapefruit juice may slightly increase the oral bioavailability and delay the onset of action of sildenafil. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In a randomized, crossover study with 24 healthy male volunteers, ingestion of 250 mL of grapefruit juice one hour before and concurrently with a 50 mg dose of sildenafil increased the mean area under the plasma concentration-time curve (AUC) of sildenafil and its pharmacologically active N-desmethyl metabolite by 23% and 24%, respectively, compared to water. Peak plasma concentrations (Cmax) were unaltered, but the time to reach sildenafil Cmax was prolonged by 0.25 hour. The observed increase in sildenafil bioavailability is unlikely to be of clinical significance in most individuals. However, pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability and may be significant in the occasional susceptible patient. Indeed, one subject in the study had a 2.6-fold increase in sildenafil concentrations.

MANAGEMENT: It may be advisable to avoid administration of sildenafil with grapefruit juice to prevent potential toxicity and delay in onset of action.

ADJUST DOSING INTERVAL: Coadministration with a high-fat meal may increase the plasma concentrations of olutasidenib. According to the product labeling, administration of a single 150 mg dose with a high-fat meal (approximately 800 to 1000 calories, with approximately 50% of those calories from fat) increased olutasidenib peak plasma concentration (Cmax) and systemic exposure (AUC) by 191% and 83%, respectively, in healthy subjects.

MANAGEMENT: Olutasidenib should be administered at about the same time each day, on an empty stomach at least 1 hour before or 2 hours after a meal.