My doc told me that Lexapro is effective at a lower dose than Celexa. I used to take 20mg Celexa and now I take 10 mg Lexapro. She gave me a long explanation of the subtle difference between the two. I just did a Google search and found sort of what she told me:

"Depression research has shown that the S enantiomer of citalopram is much more active as an antidepressant than the R enantiomer, which is why Lexapro (just the S enantiomer) was developed."

I find Lexapro to be much more effective on my anxiety. I haven't had a panic attack since I have been on it. I still had panic attacks when I took Celexa. I take a lot less Clonazepam now than I did when I was on Celexa. That might be because I'm getting better too. I can't compare their efficacy on depression because I wasn't depressed before or during the time I was on Celexa. I started taking Lexapro after being off Celexa for almost a year because I was going through a bad bout of depression.

I have no idea why I'm losing weight on Lexapro while I gained so much on Celexa -- other than the fact that I was SO lethargic on Celexa. It didn't increase my appetite; I just had no energy at all. The weight basically fell off -- 30 lbs. in 3 months -- after I stopped taking Celexa.