Both pseudoephedrine (Sudafed) and phenylephrine (Sudafed PE) are decongestants used to treat nasal congestion due to allergies, colds, sinus infections, etc. Since pseudoephedrine can be made into methamphetamines, the U.S. Senate passed a bill restricting its sale. Products containing phenylephrine can not be made into methamphetamines, so their sale is not restricted. Additional facts about the difference between Sudafed and Sudafed PE include:

• The intestines will absorb only about 38 percent of the amount of phenylephrine in one tablet while pseudoephedrine is 100 percent absorbed.
• The effects of phenylephrine do not last as long as pseudoephedrine. Therefore, phenylephrine needs to be taken every four hours while pseudoephedrine can be taken every four to six hours.