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Do not consume grapefruit or grapefruit juice during treatment with dasatinib. Grapefruit juice can significantly increase the blood levels and effects of dasatinib, which may result in excessive slowing of heart rate or other conduction disturbances and it may affect your bone marrow function, resulting in low numbers of different types of blood cells. You may be more likely to develop anemia, bleeding problems, or infections due to low blood cell counts. Talk to your doctor if you have any questions or concerns. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, heart palpitations, paleness, fatigue, unusual bruising or bleeding, fever, chills, diarrhea, sore throat, muscle aches, blood in phlegm, weight loss, pain or burning during urination, red or inflamed skin, or body sores during treatment with dasatinib. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

GENERALLY AVOID: Grapefruit and grapefruit juice may significantly increase the plasma concentrations of dasatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruit. Because grapefruit juice inhibits primarily intestinal rather than hepatic CYP450 3A4, the magnitude of interaction is greatest for those drugs that undergo significant presystemic metabolism by CYP450 3A4 (i.e., drugs with low oral bioavailability). 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. Pharmacokinetic interactions involving grapefruit juice are also subject to a high degree of interpatient variability, thus the extent to which a given patient may be affected is difficult to predict. Because dasatinib prolongs the QT interval, high plasma levels of dasatinib may increase the risk of ventricular arrhythmias such as torsade de pointes and sudden death.

MANAGEMENT: Patients treated with dasatinib should avoid consumption of grapefruit, grapefruit juice, and any supplement containing grapefruit extract. Some authorities recommend close monitoring for toxicity (e.g., myelosuppression, bleeding complications, fluid retention, bradycardia or other conduction disturbances) and a reduction of dasatinib dosage to a range of 20 to 40 mg daily should be considered if there are no alternatives and concomitant use with a potent CYP450 3A4 inhibitor is necessary.