I myself do not have experience with Lexapro, but my boyfriend (depression and anxiety) has been taking Lexapro with xanax for a few years. It worked well for him for some time. Unfortunately, its effectiveness has worn off so now he is being re-evaluated for a possible change to his dx.
I am not familiar with the specifics on side-effects he experienced and for how long they may have lasted.
I have heard from others that were BP, they do not have any affect, but also everyone has a different reaction to the drug based on their chemistry make-up.
Best of luck in your search..