At first I was switched from Anastrozole to Exemestane, which many people find of benefit as it's a steroid. Regrettably, I had a severe allergic reaction to it. A few months later, after the rash subsided, I was switched to Letrozole. It gave me extremely swollen feet and unrelenting insomnia. The feet situation was particularly troublesome as I have chemo-induced peripheral neuropathy as it is....

Having run out of AI (aromatase inhibitor) choices, my oncologist then switched me to a SERM (a selective Estrogen Receptor Modulator) called Evista (Raloxifene). SERMs most commonly are given to those who are pre-menopausal. (Tamoxifen is a well-known SERM.) SERMs act a bit differently than AI's do, and are a bit less effective than AIs, but are generally effective for those who are post-menopausal.

EVISTA has the advantage of helping build bone. One of the downsides is that it is much more expensive than an AI. (For my particular drug plan, the out-of-pocket cost is $400/year versus $28/yr for the AIs.) I've only recently started on it so I imagine that it will take a few weeks/months before I may notice any side effects... if at all.

Each of the AIs and SERMs have a long list of POSSIBLE side effects. The only way for an individual to find out is to try them and, if she experiences a side effect or more, figure out how tolerable it is and/or whether there are ways to help alleviate it.

Wishing you good luck on this medication adventure!