Drug Interaction Report

Lapatinib may increase the blood levels of revefenacin following oral inhalation. This may increase side effects such as drowsiness, blurred vision, dry mouth, heat intolerance, flushing, decreased sweating, difficulty urinating, abdominal cramping, constipation, rapid heart beat, confusion, memory problems, and glaucoma. Although serious side effects are not very common with inhaled products such as revefenacin because only limited amounts of the medication generally get absorbed into the bloodstream from the lungs, they can sometimes occur, especially in the elderly or when combined with medications that can impair its clearance from the body. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact. You should avoid activities requiring mental alertness such as driving or operating hazardous machinery until you know how these medications affect you. Also keep your eyes closed or use an eye mask during inhalation to avoid having the medication get into the eyes, which can cause blurry vision and eye pain as well as increase absorption of the medication into the bloodstream. 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.