Drug Interaction Report

Estramustine should generally not be used during treatment with letrozole. Estrogen-containing medications may counteract the action of letrozole and make it less effective in treating your condition. Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact. 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 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.

Food and milk may decrease the levels of estramustine in your body. It is recommended that estramustine be taken at least 1 hour before or 2 hours after meals. This will make it easier for your body to absorb the medication. Estramustine should not be taken with milk or calcium containing products.

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.

The recommended maximum number of medicines in the 'antineoplastic hormones' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'antineoplastic hormones' category:

• estramustine
• Kisqali Femara Co-Pack (letrozole / ribociclib)

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.