According to Sudafed.com, Sudafed uses pseudoephedrine as a nasal decongestant, while Sudafed PE uses phenylephrine or PE. Because pseudoephedrine is used illegally to make meth, the original Sudafed formula is federally regulated and can only be purchased at a pharmacy or service counter while Sudafed PE can be purchased without such restrictions and is usually found on the cold and allergy aisle.
Sudafed.com notes that the original Sudafed formula and Sudafed PE provide relief from sinus congestion and pressure temporarily. They also temporarily relieve nasal congestion caused by hay fever, upper respiratory allergies and the common cold. Adults using Sudafed are instructed to take two tablets every four to six hours without exceeding eight tablets in 24 hours, while adults using Sudafed PE are instructed to take one tablet ever four hours without exceeding six tablets in 24 hours.
Sudafed.com advises that children under six years should not take Sudafed, and children under 12 years are not to take Sudafed PE. Those taking prescription drugs contain a monoamine oxidase inhibitor should not take Sudafed or Sudafed PE. A doctor should be consulted before use if diabetes, heart disease, high blood pressure, thyroid disease or trouble urinating because of an enlarged prostate gland is present.