Please do NOT take double doses of AD's unless your dr. has told you to. It is VERY dangerous. AD's break the blood/brain barrier (it is the nature of how they work) and any changes made to AD's should not be done w/o the help of your dr.
AD's aren't designed to ease the immediate feeling of panic.
I am only saying this with such passion because I decided I knew better than my dr. how to medicate myself and even doing it a few times is very detrimental to the therapy.
AD's take several weeks (usually more than two) to reach a therapeutic level so extra doses wont help.