[teach]

You mention three different medications here:

- diphenhydramine aka Benedryl is an antihistamine with a common side effect of sleepiness

- doxylamine aka Unisom is also an antihistamine but these days people only really use it as a sleep aid or for nausea

- psuedoephedrine aka Sudafed is a decongestant. Not sold over-the-counter because it can be used to make meth. It's a stimulant and appetite supressant

Finally, there's "Sudafed PE" aka phenylephrine, which is also sold as a decongestant but it (literally) doesn't work