I am on Ibrance since last December. The only side effects I've experienced are my liver test numbers went up and on the weeks I take the pills I don't have as much energy as I do on my off weeks. I started off taking the lowest possible dose which is 75 mg per pill and I am still taking the smallest dose. At first I took the Ibrance for 3 weeks on and then would have a 1 week break before starting the next cycle. My liver test numbers from my blood tests skyrocketed. It took a few months to figure out what dose my liver could tolerate. I now take the Ibrance for 2 weeks on and then 2 weeks off before starting the next cycle and my liver is much happier now. My energy comes back after I've been off the Ibrance for a few days.

With both the CDK inhibitors and the AI meds many doctors will start patients off with the highest dose of the medications which can lead to the patient having more side effects. With both the CDK inhibitors and the AIs there have been studies done that show the smallest doses of these meds are adequate to achieve the desired effects of the medications for many patients. I also take the smallest dose of Letrozole and my only side effects are hot flashes and my lifelong insomnia has grown a bit worse.

Ask your doctor to start you off on the smallest dose and see how you do. If your doctor thinks you need to have a higher dosage ask to start off with the lower dose and work your way up to a higher dose as your body adjusts to the medication.