Drug Interactions between ceritinib and Ingrezza

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of ceritinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because ceritinib is associated with concentration-dependent prolongation of the QT interval, increased levels may potentiate the risk of ventricular arrhythmias such as torsade de pointes and sudden death. Other, more common side effects such as diarrhea, nausea, vomiting, abdominal pain, hyperglycemia, and bradycardia may also increase.

ADJUST DOSING INTERVAL: Food increases the oral bioavailability of ceritinib. The mechanism of interaction is unknown. Compared to the fast state, administration of a single 500 mg dose of ceritinib with a high-fat meal (approximately 1000 calories; 58 grams of fat) increased ceritinib peak plasma concentration (Cmax) and systemic exposure (AUC) by 41% and 73%, respectively, and administration with a low-fat meal (approximately 330 calories; 9 grams of fat) increased ceritinib Cmax and AUC by 43% and 58%, respectively. A dose of 600 mg or higher taken with a meal is expected to produce systemic exposure exceeding that from a 750 mg dose taken in the fasted state, which may lead to increased adverse effects.

MANAGEMENT: Patients treated with ceritinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Ceritinib should be administered on an empty stomach (i.e., avoid administration within 2 hours of a meal).

ADJUST DOSE: Coadministration with grapefruit juice may increase the plasma concentration of valbenazine. The mechanism is inhibition of CYP450 3A4-mediated first-metabolism in the gut wall by certain compounds present in grapefruits. The use of valbenazine has been associated with modest prolongation of the QT interval. However, clinically significant QT prolongation may occur in patients taking a strong CYP450 3A4 inhibitor due to increased concentrations of valbenazine and its active metabolite (+)-alfa-dihydrotetrabenazine. In general, the risk of an individual agent or a combination of agents causing ventricular arrhythmia in association with QT prolongation is largely unpredictable but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia). The extent of drug-induced QT prolongation is dependent on the particular drugs involved and dosages of the drugs.

MANAGEMENT: Pharmacologic response to valbenazine should be monitored more closely whenever a strong inhibitor of CYP450 3A4 is added to or withdrawn from therapy. Assessment of baseline QT interval and periodic monitoring during therapy may be considered. The manufacturer recommends reducing the dose of valbenazine to 40 mg once daily during concomitant administration with strong CYP450 3A4 inhibitors. Patients should be advised to seek prompt medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, lightheadedness, fainting, palpitation, irregular heart rhythm, shortness of breath, or syncope. In addition, patients receiving CNS-active agents should be warned of this interaction and advised to avoid or limit consumption of alcohol. Ambulatory patients should be counseled to avoid hazardous activities requiring complete mental alertness and motor coordination until they know how these agents affect them, and to notify their physician if they experience excessive or prolonged CNS effects that interfere with their normal activities.