Drug Interaction Report

Ribociclib may increase the blood levels and effects of letrozole. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. Contact your doctor if your condition changes or you experience increased side effects. 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.

Ribociclib may increase the blood levels of abemaciclib in some patients. This may increase side effects such as nausea, vomiting, diarrhea, abdominal pain, decreased appetite, mouth sores, blood clots, hair loss, liver problems, and impaired bone marrow function resulting in low numbers of different types of blood cells. 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. 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. Contact your doctor if you develop paleness, fatigue, dizziness, fainting, unusual bruising or bleeding, fever, chills, diarrhea, sore throat, muscle aches, shortness of breath, blood in phlegm, weight loss, red or inflamed skin, body sores, and pain or burning during urination. 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.

Patients should not consume pomegranates, pomegranate juice, grapefruit, or grapefruit juice during treatment with ribociclib unless directed otherwise by your doctor. Pomegranate juice or grapefruit juice can increase the blood levels of ribociclib. You may be more likely to experience side effects such as nausea; vomiting; diarrhea; loss of appetite; abdominal pain; mouth sores; hair loss; weakness; and impaired bone marrow function resulting in low numbers of different types of blood cells, which can increase the risk of anemia, bleeding problems, and infections. 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.

Grapefruit juice can increase the blood levels of abemaciclib. This may increase side effects such as nausea, vomiting, diarrhea, abdominal pain, decreased appetite, mouth sores, blood clots, hair loss, liver problems, and impaired bone marrow function resulting in low numbers of different types of blood cells. You may also be more likely to develop anemia, bleeding problems, or infections due to low blood cell counts. You should avoid the consumption of grapefruit and grapefruit juice during treatment with abemaciclib. Be sure to take the medication at approximately the same time everyday to maintain consistent blood levels and effects. Talk to your doctor or pharmacist if you have questions on how to take this or other medications you are prescribed. 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.

The recommended maximum number of medicines in the 'CDK 4/6 inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'CDK 4/6 inhibitors' category:

• letrozole / ribociclib
• Verzenio (abemaciclib)

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.