I'm taking both from 10 months ago and had a heart problem after 4 months. I consulted an oncologist in MD Anderson regarding dose reduction of Kisqali from 400mg to 200 mg. He said 200 mg will be useless. It won't work. I consulted another oncologist and was told I may take Kisqali 400 mg one day and 200 mg another day if my heart problem gets worse. I consulted my cardiologist for his suggestion. He is very experienced. He told me that both medicines may cause heart issues, so he ordered heart ultrasound for me. Fortunately the problem is not serious. He did not think I shall reduce the dose. After I take supplements like CQ 10, fish oil and drink a lot of water per day, the heart problem was gone.