Phenylephrine Hydrochloride

Phenylephrine is a medication primarily used as a decongestant, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. While marketed as a decongestant, taken by mouth at recommended doses it is of unclear benefit for hay fever. It can be taken by mouth, given by injection into a vein or muscle, or applied to the skin. Phenylephrine is a medication primarily used as a decongestant, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. While marketed as a decongestant, taken by mouth at recommended doses it is of unclear benefit for hay fever. It can be taken by mouth, given by injection into a vein or muscle, or applied to the skin. Common side effects when taken by mouth or injected include nausea, 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 activator 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. In the United Kingdom the injectable formulation costs the NHS £4 per vial. Unlike pseudoephedrine, abuse of phenylephrine is very uncommon. 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. Other decongestants include oxymetazoline and pseudoephedrine. Phenylephrine is used as an alternative for pseudoephedrine in decongestant medicines due to pseudoephedrine's use in the illicit manufacture of methamphetamine. Its efficacy as an oral decongestant has been questioned, with several recent 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. Hemorrhoids are caused by swollen veins in the rectal area. Phenylephrine can be used topically to prevent symptoms of hemorrhoids. Phenylephrine causes the constriction of vascular smooth muscle and is often used in the treatment of hemorrhoids presumably to narrow the swollen veins and relieve the attendant pain. However, veins—unlike arteries—contain less vascular smooth muscle in their walls so the mechanism by which pain relief is achieved is likely related to something other than vascular change alone. Products for treatment may also include substances that will form a protective barrier over the inflamed area, resulting in less pain when feces are passed.