Dad (83, history of strokes/seizure/throat cancer, swallowing issues, takes many meds) is trying to deal with daily coughing-up of phlegm (generally not unusual-looking), and we tried to get him to take a liquid cough medicine containing guaifenesin (glyceryl guaiacolate), but he has this particular brand burnished in his brain, likely because a pill form of it my mom (d. 2015) took is still in our cabinet.
Pills (for reasons you can ascertain above) are issues for him (what he has to take, he tries to break up, /without/ liquids, in a blender), so liquid's all that's left, but the brand he wants only makes liquids that are for multiple symptoms like sore throat, nasal congestion, etc. that I can't honestly tell if he legitimately has. He won't tell me, I'm not supposed to ask him about his symptoms.
So what I did was get a guaifenesin-only product in a store brand, and repeatedly told him that it contained the same main ingredient as the brand he was interested in, among several others, and that the brand doesn't make a guaifenesin-only product in liquid form, only caplets like what mom took.
I also said that I'd need to go back to the store to exchange the store brand liquid for something in the brand he wanted, but he rejected that idea, and as of now the store brand liquid continues to sit on the kitchen table, waiting for him to either take it or to expire (at least a year away)
My brothers, who (if their cars don't break down) take dad to health appointments, appear to trust me to take care of this issue, but the only solution I can come up with, is to call back the pharmacy where I got the liquid and ask them for help.