Phenylephrine

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Phenylephrine
Phenylephrine Structural Formula V1.svg
(R)-Phenylephrine molecule ball.png
Clinical data
Pronunciation /ˌfɛnəlˈɛfriːn,fiː-,-ɪn/
Trade names Neo-synephrine, others [1]
AHFS/Drugs.com Monograph
License data
Routes of
administration 		By mouth, in the nose, on the eye, intravenous, intramuscular
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability 38% through GI tract
Protein binding 95%
Metabolism Liver (oxidative deamination)
Onset of action Very rapid (IV); within 20 min (by mouth) [2]
Elimination half-life 2.1–3.4 h
Duration of action Up to 20 min (IV); 4 hrs (by mouth) [2]
Identifiers
  • (R)-3-[-1-hydroxy-2-(methylamino)ethyl]phenol
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard 100.000.386 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula C9H13NO2
Molar mass 167.208 g·mol−1
3D model (JSmol)
  • O[C@H](c1cc(O)ccc1)CNC
  • InChI=1S/C9H13NO2/c1-10-6-9(12)7-3-2-4-8(11)5-7/h2-5,9-12H,6H2,1H3/t9-/m0/s1 Yes check.svgY
  • Key:SONNWYBIRXJNDC-VIFPVBQESA-N Yes check.svgY
   (verify)

Phenylephrine is a medication used as a decongestant for uncomplicated nasal congestion, [3] used to dilate the pupil, used to increase blood pressure (given intravenously in cases of low blood pressure), and used to relieve hemorrhoids. [2] [4] It can be taken by mouth, as a nasal spray, given by injection into a vein or muscle, or applied to the skin. [2]

Contents

Common side effects when taken by mouth or injected include nausea, vomiting, headache, and anxiety. [2] Use on hemorrhoids is generally well tolerated. [2] Severe side effects may include a slow heart rate, intestinal ischemia, chest pain, kidney failure, and tissue death at the site of injection. [2] [4] It is unclear whether its use during pregnancy and breastfeeding is safe. [2] Phenylephrine is a selective α1-adrenergic receptor agonist with minimal to no β-adrenergic receptor agonist activity. [3] It causes constriction of both arteries and veins. [2]

Phenylephrine was patented in 1933 [5] and came into medical use in 1938. [6] It is available as a generic medication. [4] [7] [8] Unlike pseudoephedrine, abuse of phenylephrine is very uncommon. [9] Its effectiveness as a nasal decongestant has been questioned. [2] [10] [11] In 2023, a Food and Drug Administration panel concluded that the drug was ineffective as a nasal decongestant when taken orally. [12]

Medical uses

Decongestant

Phenylephrine is used as an alternative to pseudoephedrine as a decongestant, whose availability has been restricted in some countries due to a potential for use in the illicit synthesis of methamphetamine. [13] 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. [14] [15] [16]

A 2007 meta-analysis concluded that the evidence for its effectiveness is insufficient, [17] 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. [18] A 2007 study by Wyeth Consumer Healthcare notes that 7 studies available in 1976 support the efficacy of phenylephrine at a 10 mg dosage. [19] The Food and Drug Administration withdrew the indication "for the temporary relief of nasal congestion associated with sinusitis" in 2007. [2]

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. [14] [15]

Pseudoephedrine was previously much more commonly available in the United States, however, provisions of the Combat Methamphetamine Epidemic Act of 2005 placed restrictions on sale in the United States 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. [20] Phenylephrine has been off-patent for some time,[ when? ] and many generic brands are available.[ citation needed ]

In September 2023, an independent advisory committee to the US Food and Drug Administration (FDA) unanimously agreed that there is insufficient evidence showing that "orally administered phenylephrine is effective as a nasal decongestant". [21] The committee also unanimously believes that this does not need further study. The FDA responded to the committee, stating it would take its advice under advisement. [22] [23]

Hemorrhoids

Hemorrhoids are caused by swollen veins in the rectal area. [24] 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 to narrow the swollen veins and relieve the attendant pain. However, veins contain less vascular smooth muscle in their walls than arteries. 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. [25]

Phenylephrine hydrochloride at 0.25% is used as a vasoconstrictor in suppository formulations for hemorrhoid treatment. [26]

Pupil dilation

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 as a synergist when tropicamide alone is not sufficient. Narrow-angle glaucoma is a contraindication to phenylephrine use. As a mydriatic, it is available in 2.5% and 10% minims. Phenylephrine eye drops are applied to the eye after a topical anesthetic is applied. [27]

Intraocular bleeding

Phenylephrine has been used as an intracameral injection into the anterior chamber of the eye to arrest intraocular bleeding occurring during cataract and glaucoma surgery. [28]

Vasopressor

Phenylephrine is commonly used as a vasopressor to increase the blood pressure in unstable patients with hypotension, especially resulting from septic shock. Such use is common in anesthesia or critical-care practices; it is especially useful in counteracting the hypotensive effect of epidural and spinal anesthesia, as well as the vasodilating effect of bacterial toxins and the inflammatory response in sepsis and systemic inflammatory response syndrome. The elimination half life of phenylephrine is about 2.5 to 3.0 hours. [29]

Because of its vasoconstrictive effect, phenylephrine can cause severe necrosis if it infiltrates the surrounding tissues. Because of this, it should be given through a central line if at all possible. Damage may be prevented or mitigated by infiltrating the tissue with the alpha blocker phentolamine by subcutaneous injection. [30]

Side effects

Phenylephrine may cause side effects such as headache, reflex bradycardia, excitability, restlessness and cardiac arrhythmias. [2] Phenylephrine is not suggested for use in people with hypertension. [31]

Heart

The primary side effect of phenylephrine is high blood pressure. People with high blood pressure are typically advised to avoid products containing it. Because this medication is a sympathomimetic amine without β-adrenergic receptor agonist activity, it does not increase contractility force and output of the cardiac muscle. It may increase blood pressure resulting in a slow heart rate through stimulation of vascular (likely carotid) baroreceptors. A common side effect during IV administration is reflex bradycardia. [32] The low concentration eye drops do not cause blood pressure changes and the changes with the higher dose drops do not last long. [33]

Other

Prostatic hyperplasia can also be worsened by use, and chronic use can lead to rebound hyperemia. [34] People with a history of anxiety or panic disorders, or on anticonvulsant medication for epilepsy should not take this substance. The drug interaction might produce seizures. Some patients have been shown to have an upset stomach, severe abdominal cramping, and vomiting issues connected to taking this drug. [35]

Phenylephrine is pregnancy category C. Due to the lack of studies done in animals and in humans, it is not known whether there is harm to the fetus. Phenylephrine should only be given to pregnant women who have a clear need. [35]

Extended use may cause rhinitis medicamentosa, a condition of rebound nasal congestion. [36]

Interactions

The increase in blood pressure effect of phenylephrine may be increased by drugs such as monoamine oxidase inhibitors, tricyclic antidepressants, and hydrocortisone. Patients taking these medications may need a lower dose of phenylephrine to achieve a similar increase in blood pressure.

Drugs that may decrease the effects of phenylephrine may include calcium channel blockers, ACE inhibitors and benzodiazepines. Patients taking these medications may need a higher dose of phenylephrine to achieve a comparable increase in blood pressure. [37]

Pharmacology

Pharmacodynamics

Phenylephrine is a sympathomimetic drug, which means that it mimics the actions of epinephrine (commonly known as adrenaline) or norepinephrine. Phenylephrine selectively binds to α1-adrenergic receptors which causes venous and arterial vasoconstriction. [31] [38]

Whereas pseudoephedrine causes both vasoconstriction and increase of mucociliary clearance through its non-specific adrenergic activity, phenylephrine's selective α1-adrenergic receptor agonism causes vasoconstriction alone, creating a difference in their methods of action.[ citation needed ]

Pharmacokinetics

Oral phenylephrine is extensively metabolized by monoamine oxidase, [1] an enzyme that is present on the mitochondrial membrane of cells throughout the body. [39] Compared to oral pseudoephedrine, phenylephrine has a reduced and variable bioavailability; only up to 38%. [1] [40]

Related Research Articles

<span class="mw-page-title-main">Pseudoephedrine</span> Pharmaceutical drug

Pseudoephedrine (PSE) is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It may be used as a nasal/sinus decongestant, as a stimulant, or as a wakefulness-promoting agent in higher doses.

<span class="mw-page-title-main">Ephedrine</span> Medication and stimulant

Ephedrine is a central nervous system (CNS) stimulant that is often used to prevent low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred treatment. It is of unclear benefit in nasal congestion. It can be taken by mouth or by injection into a muscle, vein, or just under the skin. Onset with intravenous use is fast, while injection into a muscle can take 20 minutes, and by mouth can take an hour for effect. When given by injection it lasts about an hour and when taken by mouth it can last up to four hours.

<span class="mw-page-title-main">Xylometazoline</span> Nasal decongestant

Xylometazoline, also spelled xylomethazoline, is a medication used to reduce symptoms of nasal congestion, allergic rhinitis, and sinusitis. Use is not recommended for more than seven days. Use is also not recommended in those less than three months of age and some say not less than 6 years of age. It is used directly in the nose as a spray or drops.

<span class="mw-page-title-main">Cold medicine</span> Medication taken to relieve cold symptoms

Cold medicines are a group of medications taken individually or in combination as a treatment for the symptoms of the common cold and similar conditions of the upper respiratory tract. The term encompasses a broad array of drugs, including analgesics, antihistamines and decongestants, among many others. It also includes drugs which are marketed as cough suppressants or antitussives, but their effectiveness in reducing cough symptoms is unclear or minimal.

<span class="mw-page-title-main">Vasoconstriction</span> Narrowing of blood vessels due to the constriction of smooth muscle cells

Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessels. The process is particularly important in controlling hemorrhage and reducing acute blood loss. When blood vessels constrict, the flow of blood is restricted or decreased, thus retaining body heat or increasing vascular resistance. This makes the skin turn paler because less blood reaches the surface, reducing the radiation of heat. On a larger level, vasoconstriction is one mechanism by which the body regulates and maintains mean arterial pressure.

Dexbrompheniramine/pseudoephedrine is a combination medication that contains the antihistamine dexbrompheniramine maleate and the decongestant pseudoephedrine sulfate. It was used to treat symptoms associated with allergies and colds such as itchy and watery eyes, runny nose, nasal and sinus congestion, and sneezing. Because it contains pseudoephedrine, its purchase in the United States was severely restricted by the Combat Methamphetamine Epidemic Act of 2005 over fears that any product containing pseudoephedrine can be used to make methamphetamine.

<span class="mw-page-title-main">Loratadine</span> Antihistamine medication

Loratadine, sold under the brand name Claritin among others, is a medication used to treat allergies. This includes allergic rhinitis and hives. It is also available in drug combinations such as loratadine/pseudoephedrine, in which it is combined with pseudoephedrine, a nasal decongestant. It is taken orally.

A decongestant, or nasal decongestant, is a type of pharmaceutical drug that is used to relieve nasal congestion in the upper respiratory tract. The active ingredient in most decongestants is either pseudoephedrine or phenylephrine. Intranasal corticosteroids can also be used as decongestants and antihistamines can be used to alleviate runny nose, nasal itch, and sneezing.

<span class="mw-page-title-main">Benadryl</span> Brand of various antihistamine medications

Benadryl is a brand of various antihistamine medications used to stop allergies, whose content varies in different countries, but which includes some combination of diphenhydramine, acrivastine, and/or cetirizine.

<span class="mw-page-title-main">Sotalol</span> Medication

Sotalol, sold under the brand name Betapace among others, is a medication used to treat and prevent abnormal heart rhythms. Evidence does not support a decreased risk of death with long term use. It is taken by mouth or given by injection into a vein.

<span class="mw-page-title-main">Fexofenadine</span> Antihistamine medication

Fexofenadine, sold under the brand name Allegra among others, is an antihistamine pharmaceutical drug used in the treatment of allergy symptoms, such as hay fever and urticaria.

<span class="mw-page-title-main">Nasal spray</span> Spray that delivers medications locally in the nasal cavities or systemically

Nasal sprays are used to deliver medications locally in the nasal cavities or systemically. They are used locally for conditions such as nasal congestion and allergic rhinitis. In some situations, the nasal delivery route is preferred for systemic therapy because it provides an agreeable alternative to injection or pills. Substances can be assimilated extremely quickly and directly through the nose. Many pharmaceutical drugs exist as nasal sprays for systemic administration. Other applications include hormone replacement therapy, treatment of Alzheimer's disease and Parkinson's disease. Nasal sprays are seen as a more efficient way of transporting drugs with potential use in crossing the blood–brain barrier.

<span class="mw-page-title-main">Oxymetazoline</span> Topical decongestant

Oxymetazoline, sold under the brand name Afrin among others, is a topical decongestant and vasoconstrictor medication. It is available over-the-counter as a nasal spray to treat nasal congestion and nosebleeds, as eyedrops to treat eye redness due to minor irritation, and as a prescription topical cream to treat persistent facial redness due to rosacea in adults. Its effects begin within minutes and last for up to six hours. Intranasal use for longer than three days may cause congestion to recur or worsen, resulting in physical dependence. It is estimated that 700,000 people in Norway could be dependent on nasal sprays.

<span class="mw-page-title-main">Naphazoline</span> Chemical compound

Naphazoline is a medicine used as a decongestant, and a vasoconstrictor added to eye drops to relieve red eye. It has a rapid action in reducing swelling when applied to mucous membranes. It is a sympathomimetic agent with marked alpha adrenergic activity that acts on alpha-receptors in the arterioles of the conjunctiva to produce constriction, resulting in decreased congestion.

<span class="mw-page-title-main">Prazosin</span> Antihypertensive drug

Prazosin, sold under the brand name Minipress among others, is a medication used to treat high blood pressure, symptoms of an enlarged prostate, and nightmares related to post-traumatic stress disorder (PTSD). It is an α1 blocker. It is a less preferred treatment of high blood pressure. Other uses may include heart failure and Raynaud syndrome. It is taken by mouth.

<span class="mw-page-title-main">Rhinitis medicamentosa</span> Medical condition

Rhinitis medicamentosa is a condition of rebound nasal congestion suspected to be brought on by extended use of topical decongestants and certain oral medications that constrict blood vessels in the lining of the nose, although evidence has been contradictory.

Actifed is a registered trademark for a combination antihistamine and nasal decongestant medication used for cold and allergy symptoms. Actifed was developed in 1958 by Burroughs Wellcome & Company, later Haleon.

<span class="mw-page-title-main">Azelastine</span> Chemical compound

Azelastine, sold under the brand name Optivar among others, is a H1 receptor-blocking medication primarily used as a nasal spray to treat allergic rhinitis (hay fever) and as eye drops for allergic conjunctivitis. Other uses may include asthma and skin rashes for which it is taken by mouth. Onset of effects is within minutes when used in the eyes and within an hour when used in the nose. Effects last for up to 12 hours.

Guaifenesin/phenylephrine is a combination of the drugs guaifenesin and phenylephrine and is a preparation against the symptoms of cold, flu and allergy. Guaifenesine is an expectorant, phenylephrine is a decongestant. The drug is sold under the brand name Entex and as generic brands. Entex La is 400 mg guaifenesin and 30 mg phenylephrine hydrochloride. Entex Pse is 600 mg guaifenesin and 120 mg phenylephrine hydrochloride. Both are extended release products, meaning that the non-active ingredients are chosen to dissolve slowly to provide a prolonged therapeutic effect.

Fexofenadine/pseudoephedrine, sold under the brand name Allegra-D among others, is a fixed-dose combination medication used for the treatment of nasal congestion and other symptoms of allergies and the common cold. It contains fexofenadine, as the hydrochloride, an antihistamine; and pseudoephedrine, as the hydrochloride, a nasal decongestant.

References

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  2. 1 2 3 4 5 6 7 8 9 10 11 12 "Phenylephrine Monograph for Professionals". Drugs.com. AHFS. 2 March 2022. Retrieved 9 May 2022. However, efficacy of oral phenylephrine for this use [as a decongestant] has been questioned.
  3. 1 2 Richards E, Lopez MJ, Maani CV (2023). "Phenylephrine". StatPearls. Treasure Island, Florida: StatPearls Publishing. PMID   30521222 . Retrieved 27 April 2023.
  4. 1 2 3 Joint Formulary Committee (2018). BNF 76 : September 2018 - March 2019. London: British Medical Association, Royal Pharmaceutical Society of Great Britain. pp. 188–189. ISBN   9780857113382. OCLC   1021215075.
  5. ↑ U.S. patent 1,932,347 , application 1928, expired 1950
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  7. ↑ "Competitive Generic Therapy Approvals". U.S. Food and Drug Administration (FDA). 29 June 2023. Archived from the original on 29 June 2023. Retrieved 29 June 2023.
  8. ↑ "First Generic Drug Approvals 2023". U.S. Food and Drug Administration (FDA). 30 May 2023. Archived from the original on 30 June 2023. Retrieved 30 June 2023.
  9. ↑ "Max Strength Decongestant Tablets" (PDF). www.mhra.gov.uk. p. 10. Archived from the original (PDF) on 19 August 2019. Retrieved 10 January 2019.
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  11. ↑ Lowe D (March 2022). "The Uselessness of Phenylephrine". Science (blog).
  12. ↑ Christensen J (12 September 2023). "Popular OTC medicines for colds and allergies don't work, FDA panel says". CNN. Retrieved 8 October 2023.
  13. ↑ Presley B, Bianchi B, Coleman J, Diamond F, McNally G (July 2018). "Efficiency of extraction and conversion of pseudoephedrine to methamphetamine from tamper-resistant and non-tamper-resistant formulations". Journal of Pharmaceutical and Biomedical Analysis. 156: 16–22. doi: 10.1016/j.jpba.2018.04.016 . PMID   29684907. S2CID   13660478.
  14. 1 2 Horak F, Zieglmayer P, Zieglmayer R, Lemell P, Yao R, Staudinger H, et al. (February 2009). "A placebo-controlled study of the nasal decongestant effect of phenylephrine and pseudoephedrine in the Vienna Challenge Chamber". Annals of Allergy, Asthma & Immunology. 102 (2): 116–20. doi:10.1016/S1081-1206(10)60240-2. PMID   19230461. Phenylephrine was not significantly different from placebo in the primary end point.
  15. 1 2 Day JH, Briscoe MP, Ratz JD, Danzig M, Yao R (April 2009). "Efficacy of loratadine-montelukast on nasal congestion in patients with seasonal allergic rhinitis in an environmental exposure unit". Annals of Allergy, Asthma & Immunology. 102 (4): 328–38. doi:10.1016/S1081-1206(10)60339-0. PMID   19441605. There were no statistically significant differences between phenylephrine and placebo for any measures.
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