I was on Letrozole, then Anastrazole and back to Letrozole. I believe the side effects were pretty much the same for me. Research online revealed for Letrozole that .5 mg was effective although normal dosage is 2.5 mg. I think I posted the information for both drugs on another thread here last month. To the point, my oncologist gave me the green light to take it every other day. On top of that he gave me a 30 day vacation from the pill. He also said that after the "stay" that it took only 2 weeks to get back to full efficacy in your body. I'm 3 years out with 2 to go. I successfully fought joint pain with collagen supplements, but it's the cognitive, mood and sleep issues that only lessen with time off. My oncologist is moving across the country but said in light of my issues that I should try to find an on/off schedule that works for me including total off. He would, of course, prefer that I not choose the last option. I hope this helps.