Drug Interaction Report

Using porfimer together with avapritinib may increase the risk of a photosensitivity reaction (e.G., redness, swelling, itching, burning sensation, feeling hot, and/or blisters), following exposure to sunlight or bright indoor lights such as examination, dental or operating room lamps; floodlights; halogen lights; and unshaded light bulbs at close proximity. It is recommended that avapritinib be avoided for at least 30 days following therapy with porfimer, and until a test for residual photosensitivity shows no photosensitivity reaction within 24 hours. In some cases, it might be necessary to avoid photosensitizing medications for 90 days or longer, although it may not be feasible to interrupt some treatments for that long, especially if they are medically necessary. Exposing your skin to normal indoor lighting is helpful as it will help your body get rid of porfimer more quickly, so you do not need to stay inside in the dark. Check with your doctor to see if you should temporarily withhold any of your medications after taking porfimer or if you have any other questions. 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.