Drug Interactions between estradiol / norethindrone / relugolix and neratinib

Neratinib may significantly increase the blood levels of relugolix. This may increase the risk and/or severity of side effects such as hot flushes; weight gain; decreased sex drive; erectile function difficulties; muscle and joint pain; constipation; diarrhea; increases in glucose, triglyceride (fat), and liver enzyme levels; and decreased hemoglobin levels. It may also increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. 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. If you do have to take both medications, you should take relugolix first, then take neratinib after at least 6 hours to minimize the effects of the interaction. 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.

Neratinib may reduce the blood levels and effectiveness of norethindrone, which may make it less reliable as a form of birth control. Alternative or additional methods of birth control such as condoms should be used during treatment with neratinib and for up to 1 month after stopping treatment to avoid unintended pregnancy. Talk to your gynecologist or other healthcare professional for help in selecting an effective method of birth control that is best for you. If you take hormone replacement for menopause, you should contact your doctor if you experience increased frequency or worsening of your symptoms such as hot flashes, vaginal dryness, or abnormal bleeding. Men receiving neratinib should also use a condom during the treatment period and for 3 months after stopping treatment. 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.