Adult: Initially, up to 500 mcg via rapid injection (within 20-30 seconds), increased in increments of 100-200 mcg up to 1 mg, if necessary.
Nasal Nasal congestion
Adult: As 0.25-1% solution: Instill 2-3 drops or sprays in each nostril 4 hourly as needed for up to 3 days. Child: ≥12 years: Same as adult dose.
Ophthalmic Production of mydriasis
Adult: As 2.5 or 10% eye drop solution: Instill 1 drop to each eye prior to procedure; a drop of local anaesthetic may be administered few minutes before instillation of phenylephrine. If necessary, repeat dose once only after at least 1 hour. Max: 3 drops per eye. Child: As 2.5% eye drop solution: Instill 1 drop to each eye. Max: 3 drops per eye. As 2.5% eye drop solution: Instill 1 drop to each eye. Max: 3 drops per eye.
Oral Nasal congestion
Adult: 10 mg 4 hourly as needed for up to 7 days. Max: 60 mg daily. Child: ≥12 years: Same as adult dose.
Parenteral Hypotensive states
Adult: Mild to moderate: Initially, 2-5 mg as 1% solution via SC/IM, with further doses up to 1-10 mg after at least 15 minutes if necessary. Alternatively,100-500 mcg via slow IV inj as 0.1% solution, repeated as necessary every -15 minutes. Severe: Initially, up to 180 mcg/minute via infusion, adjusted to 30-60 mcg/minute according to response.
Rectal Haemorrhoids
Adult: As 0.25% cream/gel/ointment either as single component or in combination with other anorectal agents: Apply to clean, dry area up to 4 times daily. As 0.25% supp: Insert 1 supp up to 4 times daily. Max: 2 mg daily. Child: ≥ 12 years: Same as adult dose.
Renal Impairment
Parenteral: Hypotensive states: Dosage reduction may be needed.
Administration
Should be taken with food.
Reconstitution
IV inj: Dilute 10 mg with 99 mL 5% dextrose or 0.9% NaCl to a concentration of 100 mcg/mL. IV infusion: Add 10 mg in 500 mL 5% dextrose or 0.9% NaCl to a concentration of 20 mcg/mL.
Contraindications
Severe hypertension, ventricular tachycardia, severe hyperthyroidism. Ophthalmic (10% solution): Close-angle glaucoma. Children and elderly. Cold preparations should not be used in children <2 years. Concomitant or within 14 days of MAOI use (oral).
Special Precautions
Patients with CV disease (e.g. ischaemic heart disease, pre-existing bradycardia, partial heart block, severe coronary artery disease, heart failure, cardiogenic shock), diabetes mellitus, asthma, arteriosclerosis, aneurysm, hypertension, narrow-angle glaucoma. Renal impairment (IV). Children. Elderly. Pregnancy (especially those with history of pre-eclampsia) and lactation.
Eye drops may cause temporary blurring of vision, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor blood pressure.
Overdosage
Symptoms: Headache, nausea, vomiting, paranoid psychosis, hallucinations, seizures, cerebral haemorrhage, palpitation, paraesthesia, reflex bradycardia, cardiac arrhythmia (e.g. ventricular tachycardia and extrasystoles), sensation of fullness in the head and tingling of extremities. Management: Symptomatic and supportive treatment. α-adrenergic blockers (e.g. phentolamine) may be used to treat severe hypertension.
Drug Interactions
Concomitant use with adrenergic blocking agents (e.g. phentolamine), phenothiazine drugs (e.g. chlorpromazine) and amiodarone may cause antagonistic effects. May potentiate pressor effects of oxytocic drugs and CV depressant effects of inhalational anaesthetics (e.g. cyclopropane, halothane). May increase risk of arrythmias with cardiac glycosides and quinidine. May enhance the effects of anticholinergic drugs (e.g. TCAs). Potentially Fatal: Concomitant use with MAOIs (or within 14 days of stopping MAOIs) may result in paroxysmal hypertension and fatal hyperthermia.
Action
Description: Phenylephrine is a sympathomimetic amine that has direct effect on α-adrenergic receptors and an indirect effect of releasing norepinephrine from its storage sites. Its main effect is systemic arterial vasoconstriction. Additionally, it produces local vasoconstriction on dilated arterioles of the conjunctiva and nasal mucosa. Onset: Immediate (IV); 10-15 minutes (IM/SC); 15-20 min (oral); Ophthalmic: 15 minutes (mydriasis), 20-90 minutes (maximal mydriasis), 3-8 hours (time to recovery); ≤2 minutes (intranasal). 15-30 minutes (decongestant). Duration: Approx 20 minutes (IV); 1-2 hours (IM); approx 1 hour (SC); ≤4 hours (oral); 2.5-4 hours (intranasal, dose dependent). Pharmacokinetics: Absorption: Erratic and incomplete absorption. Readily absorbed (oral). Bioavailability: Approx 40% (oral). Time to peak plasma concentration: 0.75-2 hours; <243> 20 minutes (ophthalmic). Distribution: Rapid distribution into peripheral tissues with minimal penetration into the brain. Volume of distribution: 200-500 L (oral). Metabolism: Metabolised in the liver via sulfate conjugation (oral: 46%, mostly in gut wall; IV: 8%), oxidative deamination (oral: 24%; IV: 50%), and glucuronidation. Undergoes first-pass metabolism in the gut and liver by monoamine oxidase. Excretion: Via urine (mainly as inactive metabolites). Elimination half-life: Approx 5 minutes (α-phase); 2-3 hours (terminal phase).
Chemical Structure
Phenylephrine Source: National Center for Biotechnology Information. PubChem Database. Phenylephrine, CID=6041, https://pubchem.ncbi.nlm.nih.gov/compound/Phenylephrine (accessed on Jan. 22, 2020)
Storage
Store between 15-25˚C. Protect from light. Diluted solution: Refer to product labelling. Ophthalmic: Store between 20-25°C. Protect from light. Some products are refrigerated between 2-8˚C, refer to detailed product guidelines.
R01BA03 - phenylephrine ; Belongs to the class of systemic sympathomimetic preparations used as nasal decongestants. R01AA04 - phenylephrine ; Belongs to the class of topical sympathomimetic agents used as nasal decongestants. S01GA05 - phenylephrine ; Belongs to the class of sympathomimetics used as ophthalmologic decongestants. S01FB01 - phenylephrine ; Belongs to the class of sympathomimetics used as mydriatics and cycloplegics. C01CA06 - phenylephrine ; Belongs to the class of adrenergic and dopaminergic cardiac stimulants excluding glycosides. Used in the treatment of hypotension. R01AB01 - phenylephrine ; Belongs to the class of topical sympathomimetic combination preparations, excluding corticosteroids. Used as nasal decongestants.
References
Anon. Phenylephrine (Nasal). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/08/2018.Anon. Phenylephrine (Ophthalmic). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/08/2018.Anon. Phenylephrine (Systemic). Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 10/08/2018.Anon. Phenylephrine Hydrochloride (EENT). AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 10/08/2018.Anon. Phenylephrine. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. https://www.ahfscdi.com. Accessed 10/08/2018.Anu-Med Hard Suppository (Major Pharmaceuticals). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 09/07/2019.APJ Hemorrhoidal Ointment (APJ Laboratories Limited). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 09/07/2019.Buckingham R (ed). Phenylephrine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 03/07/2019.Joint Formulary Committee. Phenylephrine Hydrochloride. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 10/08/2018.Nasal Four Spray (Meijer Distribution Inc). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 02/07/2019.Phenylephrine Hydrochloride Injection (West-Ward Pharmaceutical Corp.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/08/2018.Phenylephrine Hydrochloride Solution/Drops (Akorn, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/08/2018.Phenylephrine Hydrochloride Tablet, Coated (AAA Pharmaceutical, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/08/2018.Phenylephrine Hydrochloride Tablet, Film-coated (Moore Medical LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 10/08/2018.
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