Drug Interaction Report

Talk to your doctor before using lapatinib together with enzalutamide. Combining these medications may reduce the blood levels and effects of lapatinib. Contact your doctor if your symptoms worsen or your condition changes during treatment with these medications. In addition, combining these medications may increase the blood levels and effects of enzalutamide. This can increase the risk and/or severity of side effects such seizure, tiredness, weakness, diarrhea, muscle or bone pain, hot flushes, swelling, tingling or prickling sensation, headache, dizziness, insomnia, anxiety, and high blood pressure. 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.