The thing that'll screw you up most is the withdrawal from the steroids. Second on that list is the aminophylline, but like you said, they're a little leery about using it now -- justifiably, considering an overdose means some nasty cardiac side-effects.

Theophylline (aminophylline) will not screw you up if you're taking a proper dose.

Prednisone and hydrocortisone and other assorted steroids will only screw you up if the withdrawal is quick and crashing, or if you've been on oral prednisone for a long period of time (think like, 20 years.)

Otherwise, there's practically nothing to worry about. If you were going to react badly to one of these drugs, you'd have reacted already, and the drugs they're using nowadays are safer than the ones used in the past.

Theophylline is chemically related to caffeine. It's a different sort of stimulant -- a Xanthine as opposed to a catecholamine, like epinephrine or Ventolin.

They're supposed to work in the same way but the jury is out on their exact method of action, as I understand.

Side effects from Theophylline often includes cardiac side-effects (in the way of funny little beats, PVCs and things like that), tremor, rapid heartbeat, and at excessive doses, even seizures.

It has been referred to as "the poison of asthmatics".

Altogether not one of the safest drugs out there, but it still has its place in difficult-to-control asthma and COPD.