Fluoxetine
"I had been taking Lexapro for years until September 2011.  I did not know what was happen to me last summer and my doctor was running all of these different tests on me.  I was fine except the Lexapro wasn't working anymore and I was having more panic attacks. This is when my medication was switched to fluoxetine. I have felt so much better since then and I haven't had any more problems."