My father-in-law, Joe, had a cold and the dr. said Benadryl was okay because it is also used to treat PD, well one dose and Joe was wired, he was not able to have the control he ususally does, he talked incessantly about stuff that made no sense to us, so we went back to the Dr. and he said Robitussion DM, we have not tried it yet, we just let the cold work it way out......what the problem is that everyone reacts so differently, we may never find a cold medicine he can handle. Good idea, good luck, Norma