What's the difference between arimidex and femara (letrozole)?

Very little: Both of these drugs are aromatase inhibitors and are used to treat post-menopausal hormone-sensitive breast cancer patients. Their chemical structure is remarkably similar. No study has ever compared these two drugs "head-to-head", so it is hard to recommend one over the other. If one of my patient's side effects are so severe that they are contemplating stopping the med, i switch to another.

3 choices: There is a 3rd aromatase inhibitor (ai) on the market called aromasin (exemestane). The structure of this ai is slightly different and it binds irreversably to aromatase, however no clinical difference is evident with this ai in comparison to the others. Furthermore, all 3 are currently available as generics.

Different companies: These drugs have different structures but act in the same way. Both are aromatase inhibitors. Arimidex (anastrozole) (generic name anastrazole) and Femara (generic name letrozole) may have different side effects in different women, as well as different costs. They can be used interchangeably.