Drug Interactions between phenytoin and sebetralstat

Consumer information for this interaction is not currently available.

GENERALLY AVOID: Coadministration with grapefruit juice may increase the plasma concentrations of sebetralstat. The mechanism is decreased clearance of sebetralstat due to inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The interaction has not been studied with grapefruit juice but has been reported for the potent CYP450 3A4 inhibitor, itraconazole. In a clinical study, sebetralstat peak plasma concentration (Cmax) and systemic exposure (AUC) increased by 2.4-fold and 5.2-fold, respectively, following concomitant administration of the potent CYP450 3A4 inhibitor, itraconazole (200 mg once daily for 6 days). In general, the effect of grapefruit juice is concentration-, dose- and preparation-dependent, and can vary widely among brands. Certain preparations of grapefruit juice (e.g., high dose, double strength) have sometimes demonstrated potent inhibition of CYP450 3A4, while other preparations (e.g., low dose, single strength) have typically demonstrated moderate inhibition. Increased exposure to sebetralstat may increase the risk and/or severity of adverse effects such as headache and QT prolongation. The use of sebetralstat alone at doses 2.5 times the maximum recommended dose has been associated with a mean increase in corrected QT (QTc) interval of 10.4 msec. Although clinical data are lacking for sebetralstat, in general, prolongation of the QT interval may increase the risk of ventricular arrhythmias such as ventricular tachycardia and torsade de pointes.

MANAGEMENT: Consumption of food or drinks containing grapefruit should generally be avoided during treatment with sebetralstat.

Phenytoin levels may decrease when the suspension is given with enteral feedings. This could lead to a loss of seizure control. You could interrupt the feeding for 2 hours before and after the phenytoin dose. Alternatively, you may give the phenytoin suspension diluted in water and flush the tube with water after administration. These would make it easier for your body to absorb the medication. However, this still may not entirely avoid the interaction and may not always be feasible. You should have your phenytoin levels checked upon starting and stopping of enteral feedings. In addition, using phenytoin together with food may alter the effects of phenytoin. Contact your doctor if you experience worsening of seizure control or symptoms of toxicity, including twitching eye movements, slurred speech, loss of balance, tremor, muscle stiffness or weakness, nausea, vomiting, feeling light-headed, fainting, and slow or shallow breathing. If your doctor does prescribe these medications together, you may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Ask your doctor before making any changes to your therapy.