Beta blockers are exactly what you want, but note that they can only provide a moderate level of effect; taking more could do bad this to blood pressure while the anti-panic effect suffers rapidly diminishing returns.

I found this out by accident after being prescribed a beta-blocker for typical blood pressure reasons while I was trying to deal with some panic-attack issues that were serious enough to need a mild benzodiazepine. After starting the beta-blocker, the need for the benzo just went away. While the benzo was effective at blocking part of the recursive/positive-feedback loop of panic, the beta-blocker was much better at preventing the feedback loop from forming at all.

Later on, a friend of mine who attended RISD mentioned that the drug of choice that was sought by all the art students was beta-blockers, so they could present their projects without all the stage fright.

/* obDisclaimer: This is not medical advice. Taking any drug can be dangerous. See a real doctor. etc */

Very interesting - also apparently the drug of choice for many musical performances as well. I've read that it doesn't necessarily calm your nerves, but rather prevents the all consuming fight or flight feeling from manifesting, ultimately curbing something like a panic attack.