Tamoxifen
"I had Stage 1 IDC Breast Cancer, diagnosed in June 2013, mastectomies in August 2013, started tamoxifen October 2013.  After experiencing stomach digestive issues I went off it in March 2014 until August, then back on and have been on it ever since.  So almost 1 year straight, but another 5 months of it before that as well.  My biggest complaint is feeling so wiped out by the end of the day.  I take it at night when going to bed, usually 10pm-ish.  Does anyone think switching the time I take the pill will matter?  I have also noticed a 5-10 pound weight gain.  I'm very active and fit - lift weights, run, do crossfit.  I have found that the side effects of this drug are forcing me to live and eat cleaner to try and reduce them."