Drug Interactions between nirogacestat and tolvaptan

Do not consume grapefruit, grapefruit juice, Seville oranges, or starfruit during treatment with nirogacestat. Doing so can significantly increase the blood levels of nirogacestat and increase the risk and/or severity of side effects such as diarrhea, liver problems, new non-melanoma skin cancers, electrolyte disturbances, and in women who can become pregnant, ovarian problems. 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.

You should avoid drinking grapefruit juice during treatment with tolvaptan. Grapefruit juice can cause too much of the medication to be in the blood. Serious nervous system side effects such as difficulty swallowing, trouble speaking, muscle weakness, trouble controlling body movements, confusion, mood changes, seizures, and coma may occur. 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.