Why is there now two different formulas for these medicines? OTC and the sames ones that you now have to ask the Pharmacist for? What is the difference? Dextromethorphan HBr & Diphenhydramine, both of these are cough suppressants what is the difference?

the one's behind the counter contain sudafed which is kept behind the counter now since people were using it to manufacture methamphetamine. it is a stronger decongestant than the ones available OTC