Hello, sorry to hear about your panic attacks and heart symptoms. It sounds like your psychiatrist is waiting for the Lexapro to kick in, which takes about 4 to 6 weeks, for it to become effective for your anxiety symptoms. As long as you only take the Xanax for a few weeks until the Lexapro takes effect, then you should be fine. If you are still concerned about the addictive potential of Xanax, then you should go and talk to your psychiatrist about prescribing Klonopin (clonazepam), which has less of an addictive potential, and also lasts longer. Good luck.