The difference between Sudafed and Sudafed PE is that Sudafed
contains pseudoephedrine and Sudafed PE contains phenylephrine.
While phenylephrine doesn't work quite as well as a decongestant,
it is the most common decongestant ingredient in cold and sinus
formulations, due to the fact that people were using
pseudoephedrine to make the illegal drug methamphetamine.