Phenylephrine or Neo-Synephrine is an α-adrenergic receptor agonist used primarily as a decongestant, as an agent to dilate the pupil and to increase blood pressure. Phenylephrine has recently been marketed as a substitute for pseudoephedrine, (e.g. Pfizer's Sudafed PE) but there are recent claims that oral phenylephrine may be no more effective as a decongestant than placebo. ^[1] In pharmacology and toxicology, a route of administration is the path by which a drug, fluid, poison or other substance is brought into contact with the body. ... Epinephrine Norepinephrine The adrenergic receptors (or adrenoceptors) are a class of G protein-coupled receptors that are targets of the catecholamines. ... Agonists An agonist is a substance that binds to a receptor and triggers a response in the cell. ... A decongestant is a broad class of drugs designed to symptomatically treat ailments affecting the respiratory system. ... The human eye The pupil is the central transparent area (showing as black). ... A sphygmomanometer, a device used for measuring arterial pressure. ... Pseudoephedrine (commonly abbreviated as PSE) is a sympathomimetic amine commonly used as a decongestant. ... Pfizer Incorporated (NYSE: PFE) is the worlds largest research-based pharmaceutical company[1].[1] The company is based in New York City. ...

Uses

Decongestant

Phenylephrine is used as a decongestant, available as an oral medicine or as a nasal spray. Phenylephrine is now the most common over-the-counter (OTC) decongestant; oxymetazoline is a more common nasal spray. ^{[citation needed]} Pseudoephedrine was historically more common, although its notoriety as a methamphetamine precursor has led some governments to restrict its sale. Over-the-counter substances, also abbreviated OTC, are drugs and other medical remedies that may be sold without a prescription and without a visit to a medical professional, in contrast to prescription only medicines (POM). ... Oxymetazoline is a topical decongestant used, in the form of Oxymetazoline hydrochloride, in products such as Nasivion, Vicks Sinex and Afrin. ... Pseudoephedrine (commonly abbreviated as PSE) is a sympathomimetic amine commonly used as a decongestant. ... This article is about the psychostimulant, d-methamphetamine. ...

Oral phenylephrine is extensively metabolised by monoamine oxidase [1], an enzyme which is present in the gastrointestinal tract and the liver. Therefore, compared to orally-taken pseudoephedrine, it has a reduced and variable bioavailability of only up to 38 percent [2] [3], and is therefore less effective than a nasal decongestant. Because phenylephrine is a direct selective α-adrenergic receptor agonist, it does not cause the release of endogenous noradrenaline like pseudoephedrine does. Therefore, phenylephrine is less likely to cause side-effects like central nervous system stimulation, insomnia, anxiety, irritability and restlessness. A few of the metabolic pathways in a cell. ... Monoamine oxidase Monoamine oxidases (singular abbreviation MAO) (EC 1. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Upper and Lower gastrointestinal tract The gastrointestinal tract (GI tract), also called the digestive tract, or the alimentary canal, is the system of organs within multicellular animals that takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... In pharmacology, bioavailability is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. ... Agonists for muscle type see Agonist (muscle) An agonist is a substance that binds to a receptor and triggers a response in the cell. ... Norepinephrine (INN)(abbr. ... A diagram showing the CNS: 1. ... This article is about the sleeping disorder. ... what up?? Anxiety is a physiological state characterized by cognitive, somatic, emotional, and behavioral components (Seligman, Walker & Rosenhan, 2001). ...

Some popular cold remedies containing phenylephrine: Canada's hot lemon Neocitran, the United Kingdom's Lemsip, and the United States' Alka-Seltzer Cold Effervescent formula, Sudafed PE Non-Drowsy Nasal Decongestant, Robitussin CF, Tylenol Sinus, and DayQuil Capsules. Acute viral nasopharyngitis, often known as the common cold, is a viral infectious disease of the upper respiratory system (nose and throat). ... Lemsip is a well-known manufacturer of cold and flu remedies in the United Kingdom and Australasia. ... This article does not cite any references or sources. ... Sudafed is a brand name and registered trademark for a family of over-the-counter (OTC) decongestants based on pseudoephedrine hydrochloride and manufactured by Pfizer Inc. ... Robitussin is a brand of cold and cough medicines produced by Wyeth Consumer Healthcare. ... Vicks DayQuil is a medicine designed to help relieve many symptoms of a cold that is to be taken orally in either liquid or LiquiCap (capsule) form, during the day. ...

As a nasal spray, phenylephrine is available in 1% and 0.5% concentrations. It suffers some rebound congestion effects, although to a lesser degree than oxymetazoline. Rebound effect is the tendency of a medication to effect a return of the symptom being treated when the medication is discontinued or when it is no longer effective. ...

Mydriatic

Phenylephrine is used as an eye drop to dilate the pupil to facilitate visualization of the retina. It is often used in combination with tropicamide. Narrow angle glaucoma is a contraindication to phenylephrine use. Tropicamide (troe-PIK-a-mide) is an acetylcholine receptor blocker. ... In medicine, a contraindication is a condition or factor that increases the risk involved in using a particular drug, carrying out a medical procedure or engaging in a particular activity. ...

Vasopressor

Phenylephrine is sometimes used as a vasopressor to increase the blood pressure in unstable patients with hypotension. Such use is more common in anesthesia or critical care practices; phenylephrine is especially useful in counteracting the hypotensive effect of epidural and subarachnoid anesthetics. It also has the advantage of not being inotropic or chronotropic, and so it strictly elevates the blood pressure without increasing the heart rate or contractility. This is especially useful if the heart is already tachycardic and/or has a cardiomyopathy. Vasopressor is a drug used to constrict the arteries and increase blood pressure. ... In physiology and medicine, hypotension refers to an abnormally low blood pressure. ... An epidural catheter after insertion. ... For the psychedelic rock band, see SubArachnoid Space. ... Anesthesia (AE), also anaesthesia (BE), is the process of blocking the perception of pain and other sensations. ... An inotrope is an agent which increases or decreases the force or energy of muscular contractions. ... Chronotropic effects (from chrono-, meaning time) are those that change the heart rate. ...

Side effects

The primary side effect of phenylephrine is hypertension. Patients with congestion and hypertension are typically advised to avoid products containing phenylephrine. For other forms of hypertension, see Hypertension (disambiguation). ...

Pregnancy

Phenylephrine is in the FDA pregnancy category C. The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. ...

Legal issues

Pseudoephedrine and phenylephrine are both used as decongestants; and until recently, pseudoephedrine was much more commonly available in the United States. This has changed because provisions of the Combat Methamphetamine Epidemic Act of 2005 placed restrictions on the sale of pseudoephedrine products to prevent the clandestine manufacture of methamphetamine. Since 2004, phenylephrine has been increasingly marketed as a substitute for pseudoephedrine; some manufacturers have changed the active ingredients of products to avoid the restrictions on sales. ^[2] Phenylephrine has been off patent for a long time; there are many generic brands available. Pseudoephedrine (commonly abbreviated as PSE) is a sympathomimetic amine commonly used as a decongestant. ... The Combat Methamphetamine Epidemic Act of 2005 (CMEA) was signed into United States law on March 9, 2006 to regulate, among other things, retail over-the-counter sales of ephedrine, pseudoephedrine, and phenylpropanolamine products. ... Clandestine chemistry generally refers to chemistry carried out in illegal drug laboratories, but can include any kind of laboratory operation carried on in secret. ... This article is about the psychostimulant, d-methamphetamine. ... Year 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... For other uses, see Patent (disambiguation). ...

Questions about effectiveness

Pharmacists Leslie Hendeles and Randy Hatton of the University of Florida suggested in 2006 that oral phenylephrine is ineffective as a decongestant at the 10mg dose used, arguing that the studies used for the regulatory approval of the drug in the United States in 1976 were inadequate to prove effectiveness at the 10mg dose and safety at higher doses. ^[3] Other pharmacists have expressed concerns over phenylephrine's effectiveness as a nasal decongestant ^[1] and other clinicians have indicated concern for regulatory actions that reduce the availability of pseudoephedrine. ^{[4] [5]} A subsequent metaanalysis by the same researchers concluded that there is insufficient evidence for its effectiveness. ^[6] The matter is still under debate, though the Food and Drug Administration has stood by its 1976 approval. ^[2] The University of Florida (Florida, UFL, or UF) is a public land-grant, space-grant, research university located in Gainesville, Florida. ... “FDA” redirects here. ...

References

http://www.theannals.com/cgi/content/abstract/aph.1H679v1

1. ^ ^{a b} UF press release on the Hendles letter
2. ^ ^{a b} Hilenmeyer, K. All stuffed up Southwest Florida Herald-Tribune (30 January 2007)
3. ^ Heldeles, L. and Hatton, R. Oral phenylephrine: An ineffective replacement for pseudoephedrine? Journal of Allergy and Clinical Immunology, Volume 118, Issue 1, Pages 279-280
4. ^ Eccles, R. Phenylephrine an ineffective replacement for pseudoephedrine in response to the methamphetamine problem in the USA. bmj.com. (May 2006)
5. ^ Eccles, R. Substitution of phenylephrine for pseudoephedrine as a nasal decongeststant. An illogical way to control methamphetamine abuse. British Journal of Clinical Pharmacology 63. p10. (January 2007)
6. ^ Hatton, R.C. et al. Efficacy and Safety of Oral Phenylephrine: A Systematic Review and Meta-Analysis Annals of Pharmacotherapy (published online Jan 2007)

See also

• Drugs.com - Phenylephrine
• MedlinePlus DrugInfo uspdi-202460