I had a terrible time on tamoxifen. The symptoms just kept compounding and ran the spectrum from being uncomfortable - leg cramps, sleeplessness, to being dangerous - fainting and heart issues (there had no prior history). It finally culminated in a full-on allergic reaction and that's when my oncologist and I both agreed that this wasn't the drug for me. She put me on Toremifene instead; she described it as a Tamoxifen that was enzyme-processed. It's been months now and although I do think it impacts my sleep somewhat and I feel like my joints are a bit more "creaky" if I don't remember to stretch and move regularly, these are side effects that I can tolerate.