You have described my symptoms - very similar. Little less than 4 weeks on Versenio 150MG twice a day. I am 73 very healthy woman with breast cancer reoccurrence after 30 years (previous mastectomy/tamoxifen) - found a lump under my arm which was the breast cancer returned in the lymph node stage 3, estrogen positive. Refused Chemo due to my age, started on Antrolosa in April 2024 to shrink the cancer, which it did with limited side affects. Had surgery and they removed 27 lymph nodes/11 were cancerous. Then had 16 treatments of radiation as mop up. Recovered nicely from surgery/radiation - then oncologists determined I should take one of CDK 4/6 and continue to take Antrolosa. I elected to take Verenio since was a two year regime instead of three. I thought I was tough enough to handle but Versenio crushed me with headaches, fatigue, indigestion that included diarrhea and constipation, horrible lower stomach pains that moved from the front to the back - often could not stand straight, felt faint, unable to sleep due to the stomach pain - the mental fog was completely surprising and was delipating - have never been so depressed and unable to function. Even friends said I was an altered person they had a hard time recognizing. Two days ago stopped the Verenio - they are suggesting one week off then they will lower the MG - frankly after two days off the symptoms and fog clearing I am inclines to say NO to any CDK 4/5 drug. Even if this drug provides a better chance of stopping a reoccurrence, feel life is not worth living feeling even if symptoms reduced - simply no quality of life which was my primary reason from rejecting Chemo - this is chemo in pill form and very difficult to tolerate at my age. Would appreciate any information - so distressed thinking about going back on a lower dose of Verenio.