Drug Interaction Report

Lapatinib may increase the blood levels of avapritinib in some patients. This may increase the risk and/or severity of serious side effects such as bleeding in the brain; cognitive impairment (forgetfulness, confusion, trouble thinking); changes in mood or behavior; hallucinations; fluid retention or swelling; and decreases in blood cell counts. You may also 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. Your doctor may be able to prescribe alternatives that do not interact, or you may need a dose adjustment or more frequent monitoring to safely use both medications. 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.

Avapritinib should be taken on an empty stomach, one hour before or two hours after a meal. Do not consume grapefruit, grapefruit juice, or any supplements that contain grapefruit extract during treatment with avapritinib unless directed otherwise by your doctor. Grapefruit juice can increase the blood levels of avapritinib. This may increase the risk and/or severity of serious side effects such as bleeding in the brain; cognitive impairment (forgetfulness, confusion, trouble thinking); changes in mood or behavior; hallucinations; fluid retention or swelling; and decreases in blood cell counts. You may also 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. 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.

Take lapatinib on an empty stomach 1 hour before or 1 hour after a meal unless otherwise directed by your doctor. This will make it easier for your body to absorb the medication. The lapatinib dose is administered once daily and should not be divided. The usual dose of lapatinib is equal to 5 tablets. You may swallow each tablet one at a time, but take the entire lapatinib dose at the same time each day. If you are receiving therapy with lapatinib you should be advised to avoid grapefruits and grapefruit juice. Grapefruit can raise the levels of lapatinib in your body and lead to dangerous side effects.