If anyone is looking for an as-needed medication that stops panic attacks but with few side effects, I'd like to suggest Atarax. It's actually an antihistamine, originally made for allergies, but is prescribed for anxiety because it's a sedative as well.

I was originally prescribed this when I was having very severe panic attacks multiple times daily (couldn't leave my room, go to school etc) when I was 15. I believe they prescribed them as opposed to something like Xanax because I was at my GP and not a psychiatrist, plus I was young. They sent me to a psychiatrist after that for an official diagnosis and prescription refills. They offered to have me try Lexapro, but I decided to stick with the Atarax and talk therapy.

Within a few days I was able to attend school again, and about a week later I was able to hangout with my friends again (with difficulty). I stopped having regular panic attacks by about a year from then, and now at 18 I have almost no symptoms, and when I do (every few months or so), an Atarax or two will typically stop it. I'm very pleased with how my treatment went, since there was definitely a time where I thought I'd have to drop out of school or something.