Drug Interaction Report

Lapatinib can increase the blood levels of sirolimus protein-bound. This may increase side effects such as mouth sores and inflammation, nausea, diarrhea, vomiting, abdominal pain, decreased appetite, increased blood sugar, rash, hair loss, lung or breathing problems, and impaired bone marrow function resulting in low numbers of different types of blood cells. 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.

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.

Grapefruit juice may increase the blood levels of sirolimus protein-bound. However, this has not been studied, and it is not known to what extent grapefruit juice may interact with sirolimus protein-bound. High blood levels of sirolimus protein-bound can increase side effects such as mouth sores and inflammation, nausea, diarrhea, vomiting, abdominal pain, decreased appetite, increased blood sugar, rash, hair loss, lung or breathing problems, and impaired bone marrow function resulting in low numbers of different types of blood cells. You may also be more likely to develop anemia, bleeding problems, or infections due to low blood cell counts. The manufacturer recommends avoiding grapefruit and grapefruit juice during treatment with sirolimus protein-bound. 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.