Hey HeatherWelcome to BCNA website. I am so glad you have found us. Sounds like you have had a rough trot you poor luv. I sometimes wish I had opted for mastectomies cause there is always that fear of recurrence.I was originally put on Arimidex and I couldn't function at all between tiredness and major major hot flushes to the degree of being wringing wet all the time in the middle of winter while I was going through my 7 weeks of radiotherapy. They eventually took me off of that and I have been on Femara of which I am having a break from and will have to go back on next week.I am not sure about Tamoxifin but I know there is a lot of ladies on this site who are on Tamoxifin who will be able to give you some feedback. Have your doctors suggested to you why you were so tired on the Arimidex and do they feel you will be the same on Tamoxifin?Wishing you all the best with whatever plan your medical team decides for you and I hope you will be able to cope better on the new drug and that the rest of your treatment is smooth sailing. Sounds like you need a bit of good luck on your side now so I am sending you good vibes and hoping it comes your way now.Lots of love always, Mich xoxoxoxox