My oldest son used to get panic attacks that were horrifying to him when they first started. I had experienced them, but I would much rather have something wrong with ME than anything wrong with my kids. He dissolved a xanax under his tongue and the effects were immediate, he would start to breathe slower as the xannie melted.
It didn't take affect faster. The placebo effect or rather, the knowledge that he was NOT dying and relief was at hand, made the attacks much easier to manage.
He doesn't have them anymore, which is good because his wedding is Dec 10. He doesn't have to worry about panicking like he would have in his teen years. (He's 32.)