Lexapro is an SSRI with very good effectiveness for anxiety disorders (including panic), so I wouldn't think that this would be a side effect of the medication. That said, how long have you been taking it, and do you take it every day?
Okay - thank you. Basically, if you've only been taking the medication for a short time, there will be a period of adjustment that your body goes through - this could include certain physical sensations (dizziness, for example), that could actually be triggering to your panic in the short run. Some people can be very sensitive to these cues. So, if you haven't been on an SSRI before, they may be unexpected and a little disorienting. That said, Lexapro (excitalopram) takes several weeks to build up to it's full effectiveness. By that time you should see a substantial decrease in your anxiety.
However, if you can't wait for those sensations to pass (or the panic is unbearable), talk to your physician about decreasing your dose to build up more slowly (some people halve their tablets). Alternatively, you could talk to your physician about taking the dose at night, which may circumvent the physical sensations you're having because it will be during sleep.
One more thought - you could also request a temporary anti-anxiolytic (like Buspar or Ativan) on an as-needed basis until you get used to the medication. It's not good for long-term use, but it might help ease you through any side-effects that an SSRI could cause. If you're sensitive to medications and physical sensations, this might work well for you. (Some patients try over-the-counter Benadryl because of it's sedating effect - beware though, it will make you sleepy).
- - - Please let me know if this info works for you, and if you're doing alright. I know it's around that time of day (at least on the West Coast) that you have some problems. Just checking in.