Drug Interactions between Fareston and letrozole / ribociclib

You should avoid drinking grapefruit juice during treatment with toremifene. Grapefruit juice may increase the blood levels of toremifene. This can make you more likely to develop side effects such as vaginal bleeding, blood clots, or an irregular heart rhythm that may be serious or life-threatening. Contact your doctor if you experience potential signs and symptoms of blood clots such as chest pain, shortness of breath, sudden loss of vision, and pain, redness or swelling your arms or legs. You should also seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, or fast or pounding heartbeats during treatment with toremifene.

Talk to your doctor before using toremifene with soy products. There is some evidence that substances present in soy may stimulate breast tumor growth and interfere with the action of toremifene, although this has not been proven. Whether soy products are effective for hot flashes is also uncertain. 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.

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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.

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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:

• Fareston (toremifene)
• 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.