Which class of drugs acting on the autonomic nervous system would be expected to cause difficulty urinating?
And which class of drugs would exacerbate a patients suffering Shy-Drager syndrome symptoms?
I hope I'm not doing your homework for you... but:
urination is under both parasympathetic and sympathetic control. So drugs that inhibit the action of autonomic receptors (alpha-adrenergic, beta-adrenergic, nicotinic, muscarinic) could both cause difficulty urinating (although I think this would be a severe side effect) and exacerbate the symptoms of someone with Shy-Drager disease.
do a search of drugs that are alpha-adrenergic antagonists, beta-adrenergic antagonists, etc and you'll find some specific examples.