Phenylephrine is a medication primarily used as a decongestant, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. It was long maintained that when taken orally as a decongestant, it relieves nasal congestion due to colds and hay fever. Phenylephrine can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, or applied to the skin.Common side effects when taken by mouth or injected include nausea, vomiting, headache, and anxiety. Use on hemorrhoids is generally well tolerated. Severe side effects may include a slow heart rate, intestinal ischemia, chest pain, kidney failure, and tissue death at the site of injection. It is unclear if use during pregnancy or breastfeeding is safe. Phenylephrine is a selective α1-adrenergic receptor agonist which results in the constriction of both arteries and veins.Phenylephrine was patented in 1927 and came into medical use in 1938. It is available as a generic medication. Unlike pseudoephedrine, abuse of phenylephrine is very uncommon.As of 2022, there is push back on the effectiveness of phenylephrine as a decongestant, often fused with the supposition that phenylephrine is coasting on its historical status within the Food and Drug Administrations regulatory sphere as an established substitute for the proven use of pseudoephedrine as a decongestant, whose availability has been restricted by law due to its use in the illicit synthesis of methamphetamine. Medical uses
Decongestant
Phenylephrine is used as a decongestant sold as an oral medicine or as a nasal spray.
It is a common ingredient in over-the-counter decongestants in the United States.Phenylephrine is used as an alternative for pseudoephedrine in decongestant medicines due to pseudoephedrines use in the illicit manufacture of methamphetamine. Its efficacy as an oral decongestant has been questioned, with several independent studies finding that it provided no more relief to sinus congestion than a placebo.A 2007 meta-analysis concluded that the evidence for its effectiveness is insufficient, though another meta-analysis published shortly thereafter by researchers from GlaxoSmithKline found the standard 10-mg dose to be more effective than a placebo; however, the fact that GSK markets many products containing phenylephrine has raised some speculation regarding selective publishing and other controversial techniques. A 2007 study by Wyeth Consumer Healthcare notes that 7 studies available in 1976 support the efficacy of phenylephrine at a 10 mg dosage.Two studies published in 2009, examined the effects of phenylephrine on symptoms of allergic rhinitis by exposing people to pollen in a controlled, indoor environment. Neither study was able to distinguish between the effects of phenylephrine or a placebo. Pseudoephedrine and loratadine–montelukast therapy were found to be significantly more effective than both phenylephrine and placebo.The Food and Drug Administration withdrew the indication "for the temporary relief of nasal congestion associated with sinusitis" in 2007.Pseudoephedrine was previously much more commonly available in the United States, however, provisions of the Combat Methamphetamine Epidemic Act of 2005 placed restrictions on the sale of pseudoephedrine products to prevent the clandestine manufacture of methamphetamine.