Phenylephrine hydrochloride is an α-agonist used medically to increase blood pressure, as a nasal decongestant and also to dialate the pupil.

Although pseudoephedrine is much more commonly used as a nasal decongestant in the United States, because of the possibility that pseudoephedrine can be used in the clandestine manufacture of methamphetamine, it is expected that phenylephrine will become more common. In particular, Pfizer, who manufactures the name brand decongestant Sudafed introduced a new formulation in late 2004, "Sudafed PE," that uses phenylephrine instead of pseudoephedrine.

Pfizer was a strong opponent of strict pseudoephedrine laws previous to their introduction of "Sudafed PE", but now that their product is widely available (and currently the primary non-pseudoephedrine decongestant formula), they have changed their position to support legal changes severely restricting the sale of pseudoephedrine products.

The popular Canadian hot lemon cold remedy Neo Citran has contained phenylephrine for a number of years.

Phenylephrine is in the FDA pregnancy category C. This means that it is not known whether it will harm an unborn baby. Do not use this medication without first talking to your doctor if you are pregnant or nursing.