When doc's won't give is stuff to suppress the cough I feel it is more because most of these meds also dehydrate sections, EG pseudoephedrine or guaifenesin. I am not familair with OTC drugs I am unsure about all the different tussin productss. There are different types so get the one without the decongestant, I imagine that would be plain ol 'tussin. If you had a friend that is a doc maybe get a cough syrup with codiene or phenergan, that is what you really would want, suppress your cough all the while knocking you out.
Luke 29 w/cf and brother that is a sad sad steeler fan, go cowboys!.