Version July 2025
Hypotension or shock: Note: Not recommended for septic shock except in the following circumstances: 1) when norepinephrine (preferred first-line agent) is associated with serious arrhythmias; 2) when cardiac output is known to be high and BP persistently low; or 3) used as salvage therapy when the combination of vasopressor/inotropic agents and low-dose vasopressin fail to achieve target mean arterial pressure (MAP) (Ref). In general, maintain goal MAP (eg, ~65 mm Hg); consider use if patient is in shock or has hypoperfusion during or after fluid resuscitation (Ref). Institutional protocols may vary with weight-based or non–weight-based dose regimens.
Septic shock and other vasodilatory shock states (alternative agent):
Weight-based dosing: Continuous infusion: IV: Initial dose: 0.5 to 2 mcg/kg/minute; titrate to desired MAP; usual dosage range: 0.25 to 5 mcg/kg/minute. Doses up to 9.1 mcg/kg/minute have been reported (Ref).
Non–weight-based dosing (based on ~80 kg patient): Continuous infusion: IV: Initial dose: 40 to 160 mcg/minute; titrate to desired MAP; usual dosage range: 20 to 400 mcg/minute. Doses up to ~730 mcg/minute have been reported (doses calculated and rounded for an 80 kg patient according to weight-based dosing using the referenced sources (Ref)).
Cardiogenic shock: Note: Depending on hemodynamic variables, may consider for vasoactive management of cardiogenic shock due to aortic stenosis, mitral stenosis, or hypertrophic cardiomyopathy with left ventricular outflow tract obstruction (Ref).
Continuous infusion: IV: 0.1 to 10 mcg/kg/minute; titrate to clinical end point (Ref).
Hypotension during anesthesia:
IV bolus: Initial: 40 to 100 mcg/dose; may repeat every 1 to 2 minutes as needed; titrate to clinical end point; maximum total dose: 200 mcg.
Continuous infusion: IV: Initial dose: 10 to 35 mcg/minute; titrate to clinical end point; maximum dose: 200 mcg/minute.
Nasal congestion: Oral: OTC labeling: 10 mg every 4 hours as needed for ≤7 days (maximum: 60 mg/24 hours).
Priapism, acute ischemic (off-label use): Note: The optimal dosing, frequency, and method of administration has not been established.
Intracavernous (off-label route): 100 to 500 mcg every 5 minutes or greater as needed for up to 1 hour (using a concentration of 100 to 500 mcg/mL); if used with aspiration/irrigation, then aspiration should be performed before administration of phenylephrine (Ref).
Mild to severe impairment: There are no dosage adjustments provided in the manufacturer's labeling.
End-stage kidney disease: There are no dosage adjustments provided in the manufacturer's labeling; dose-response data indicate increased responsiveness; lower initial doses may be required.
There are no dosage adjustments provided in the manufacturer's labeling; dose-response data indicate decreased responsiveness; higher doses may be required.
The recommendations for dosing in patients with obesity are based upon the best available evidence and clinical expertise. Senior Editorial Team: Jeffrey F. Barletta, PharmD, FCCM; Manjunath P. Pai, PharmD, FCP; Jason A. Roberts, PhD, BPharm (Hons), B App Sc, FSHP, FISAC.
Class 1, 2, and 3 obesity (BMI ≥30 kg/m2):
Continuous infusion: IV: If institution uses weight-based dosing, use ideal body weight for initial weight-based dose calculations, then titrate to hemodynamic effect and clinical response (Ref). If institution uses nonweight-based dosing for vasoactive agents, continue with this approach. During therapy, clinicians should not change dosing weight from one weight metric to another (ie, ideal body weight to/from actual body weight or weight-based dosing to/from nonweight-based dosing) (Ref). Refer to adult dosing for indication specific doses.
Rationale for recommendations: There is a paucity of studies evaluating the influence of obesity on phenylephrine dosing or pharmacokinetics. Observational studies, including phenylephrine, epinephrine, and norepinephrine, suggest nonweight-based dosing strategies may result in lower overall cumulative dose requirements and increased drug exposure to second line agents in some patients and may not be advantageous in time to achieving hemodynamic stability (Ref). However, it is difficult to show outcome differences between weight-based and nonweight-based dosing because of dose titration to target BP, particularly in the context of retrospective studies. Furthermore, there is substantial variability in response in critically ill patients, irrespective of weight. Due to the short onset of action and small Vd, rapid titration to clinical effect after initial dosing is possible (Ref).
Refer to adult dosing.
(For additional information see "Phenylephrine (systemic): Pediatric drug information")
Note: Dosing presented in both mg (oral) and mcg (parenteral); use caution when ordering and dispensing.
Nasal congestion: Oral:
Children 4 to 5 years: 2.5 mg every 4 hours; maximum daily dose: 15 mg in 24 hours.
Children 6 to 11 years: 5 mg every 4 hours; maximum daily dose: 30 mg in 24 hours.
Children ≥12 years and Adolescents: 10 mg every 4 hours; maximum daily dose: 60 mg in 24 hours.
Hypotension, low cardiac output: Limited data available: Infants, Children, and Adolescents:
IM, SubQ: 100 mcg/kg/dose every 1 to 2 hours as needed; maximum dose: 5,000 mcg/dose (Ref).
IV bolus: 5 to 20 mcg/kg/dose every 10 to 15 minutes as needed (Ref); initial dose should not exceed 500 mcg/dose.
Continuous IV infusion: Usual initial dose: 0.1 to 0.5 mcg/kg/minute; titrate to desired response (Ref); in cases of shock or intraoperative hypotension, doses up to 2 mcg/kg/minute have been reported (Ref); for management of infundibular spasm (tet spell), even higher doses up to 5 mcg/kg/minute may be required (Ref).
Hypotension during spinal anesthesia: IM, SubQ: Infants, Children, and Adolescents: 44 to 88 mcg/kg/dose; maximum dose: 500 mcg.
Mild to severe impairment: There are no dosage adjustments provided in the manufacturer's labeling.
End-stage renal disease: There are no dosage adjustments provided in the manufacturer's labeling. Based on dose-response data, a lower initial dose is recommended.
There are no dosage adjustments provided in the manufacturer's labeling.
The following adverse drug reactions are derived from product labeling for IV use, unless otherwise specified.
Postmarketing:
Cardiovascular: Atrioventricular block, bradycardia, cardiac arrhythmia, cardiomyopathy (oral; takotsubo) (Zlotnick 2012), chest pain, hypertension, hypertensive crisis, ischemia, ischemic heart disease, low cardiac output, premature ventricular contractions, reflex bradycardia
Dermatologic: Diaphoresis, pallor, piloerection, pruritus
Gastrointestinal: Epigastric pain, ischemic colitis (oral) (El-Alali 2020), nausea, vomiting
Hypersensitivity: Hypersensitivity reaction (sulfite sensitivity; including anaphylaxis) (Pathan 2024))
Local: Localized blanching
Nervous system: Cerebrovascular accident (IV, oral; including cerebral hemorrhage) (Tark 2014), excitability, headache, nervousness, paresthesia, tremor
Neuromuscular & skeletal: Neck pain
Ophthalmic: Blurred vision
Respiratory: Dyspnea, pulmonary edema, rales
Immphentiv: Hypersensitivity to phenylephrine or any component of the formulation.
OTC labeling (Oral): When used for self-medication: Use with or within 14 days of monoamine oxidase inhibitor therapy.
Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Concerns related to adverse effects:
• Cardiovascular effects: IV use of phenylephrine may cause severe bradycardia (likely baroreflex mediated) and reduced cardiac output due to an increase in cardiac afterload especially in patients with preexisting cardiac dysfunction (Goertz 1993; Yamazaki 1982). May also precipitate angina in patients with severe coronary artery disease and increase pulmonary arterial pressure. Use with caution in patients with preexisting bradycardia, partial heart block, myocardial disease, or severe coronary artery disease. Avoid or use with extreme caution in patients with heart failure or cardiogenic shock; increased systemic vascular resistance may significantly reduce cardiac output. Avoid use in patients with hypertension (contraindicated in severe hypertension); monitor BP closely and adjust infusion rate. May also cause excessive peripheral and visceral vasoconstriction and ischemia to vital organs, particularly in patients with extensive peripheral vascular disease.
• Extravasation: IV administration: Vesicant; ensure proper needle or catheter placement prior to and during infusion. Avoid extravasation.
Disease-related concerns:
• Acidosis: Acidosis may reduce the efficacy of phenylephrine; correct acidosis during use of phenylephrine.
• Autonomic dysfunction: Patients with autonomic dysfunction (eg, spinal cord injury) may exhibit an exaggerated increase in BP response to phenylephrine.
Concurrent drug therapy issues:
• Monoamine oxidase inhibitors: Use with extreme caution in patients taking monoamine oxidase inhibitors; hypertension may result from concurrent use.
Dosage form specific issues:
• Benzyl alcohol and derivatives: Some dosage forms may contain sodium benzoate/benzoic acid; benzoic acid (benzoate) is a metabolite of benzyl alcohol; large amounts of benzyl alcohol (≥99 mg/kg/day) have been associated with a potentially fatal toxicity (“gasping syndrome”) in neonates; the “gasping syndrome” consists of metabolic acidosis, respiratory distress, gasping respirations, CNS dysfunction (including convulsions, intracranial hemorrhage), hypotension, and cardiovascular collapse (AAP ["Inactive" 1997]; CDC 1982); some data suggest that benzoate displaces bilirubin from protein binding sites (Ahlfors 2001); avoid or use dosage forms containing benzyl alcohol derivative with caution in neonates. See manufacturer's labeling.
• Oral: When used for self-medication (OTC), use with caution in patients with asthma, bowel obstruction/narrowing, hyperthyroidism, diabetes mellitus, cardiovascular disease, ischemic heart disease, hypertension, increased intraocular pressure, prostatic hyperplasia, or in older adults. Notify health care provider if symptoms do not improve within 7 days or are accompanied by fever. Discontinue and contact health care provider if nervousness, dizziness, or sleeplessness occur.
• Sulfites: Some products contain sulfites, which may cause allergic reactions in susceptible individuals.
Other warnings/precautions:
• Appropriate use: When used IV in patients who are hypotensive, assure adequate circulatory volume to minimize need for vasoconstrictors.
Safety and efficacy for the use of cough and cold products in pediatric patients <4 years of age is limited; the AAP warns against the use of these products for respiratory illnesses in young children. Serious adverse effects including death have been reported. Many of these products contain multiple active ingredients, increasing the risk of accidental overdose when used with other products. The FDA does not recommend OTC uses for these products in pediatric patients <2 years of age and recommends to use with caution in pediatric patients ≥2 years of age. Health care providers are reminded to ask caregivers about the use of OTC cough and cold products in order to avoid exposure to multiple medications containing the same ingredient (AAP 2018; CDC 2007; FDA 2017; FDA 2018).
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Solution, Intravenous, as hydrochloride:
Immphentiv: 0.5 mg/5 mL (5 mL); 1 mg/10 mL (10 mL) [contains edetate (edta) disodium]
Vazculep: 10 mg/mL (1 mL [DSC], 5 mL, 10 mL) [contains sodium metabisulfite]
Generic: 10 mg/mL (1 mL, 5 mL, 10 mL)
Solution, Intravenous, as hydrochloride [preservative free]:
Biorphen: 0.5 mg/5 mL (5 mL)
Biorphen: 0.5 mg/5 mL (5 mL [DSC]) [sulfate free]
Generic: 10 mg/mL (1 mL, 5 mL, 10 mL)
Solution, Oral, as hydrochloride:
Sudafed PE Childrens: 2.5 mg/5 mL (118 mL) [alcohol free, sugar free; contains edetate (edta) disodium, fd&c red #40 (allura red ac dye), sodium benzoate; berry flavor]
Tablet, Oral, as hydrochloride:
FT Nasal Decongestant PE: 10 mg [pseudoephedrine free; contains fd&c red #40 (allura red ac dye)]
Medi-Phenyl: 5 mg [pseudoephedrine free; contains fd&c red #40 (allura red ac dye), fd&c yellow #6 (sunset yellow)]
Non-Pseudo Sinus Decongestant: 10 mg [contains fd&c red #40(allura red ac)aluminum lake, fd&c yellow #6(sunset yellow)alumin lake]
Sudafed PE Sinus Congestion: 10 mg [contains fd&c red #40(allura red ac)aluminum lake, fd&c yellow #6(sunset yellow)alumin lake, quinoline (d&c yellow #10) aluminum lake]
Sudanyl PE: 5 mg [antihistamine free, caffeine free, salt free, sugar free; contains fd&c red #40 (allura red ac dye), fd&c yellow #6 (sunset yellow)]
Generic: 10 mg
Yes
Solution (Biorphen Intravenous)
0.5 mg/5 mL (per mL): $1.20
Solution (Immphentiv Intravenous)
0.5 mg/5 mL (per mL): $1.20
1 mg/10 mL (per mL): $1.20
Solution (Phenylephrine HCl (Pressors) Intravenous)
10 mg/mL (per mL): $1.36 - $4.80
Solution (Sudafed PE Childrens Oral)
2.5 mg/5 mL (per mL): $0.05
Solution (Vazculep Intravenous)
10 mg/mL (per mL): $5.30
Tablets (Phenylephrine HCl Oral)
10 mg (per each): $0.04
Tablets (Sudafed PE Sinus Congestion Oral)
10 mg (per each): $0.41
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product
Solution, Injection, as hydrochloride:
Neo-Synephrine: 10 mg/mL ([DSC]) [contains sodium metabisulfite]
Generic: 10 mg/mL (1 mL, 2 mL, 5 mL, 10 mL)
Solution Prefilled Syringe, Intravenous, as hydrochloride:
Generic: 0.5 mg/10 mL (10 mL)
IV:
Hypotension/shock: May be administered via continuous infusion (after diluting); IV infusions require an infusion pump. When administering as a continuous infusion, central line administration is preferred; extravasation may cause severe ischemic necrosis. If central line is not available, may administer for a short duration (<72 hours) through a peripheral IV catheter placed in a large vein at a proximal site (eg, in or proximal to antecubital fossa). Frequent monitoring of the IV catheter site is recommended to rapidly identify extravasation (Ref). Refer to institutional policies and procedures; catheter placement/size and vasopressor concentration may vary depending on institution. Administration through midline catheters may also be an option (Ref).
Hypotension during anesthesia: Using 100 mcg/mL concentration, administer as an IV bolus over 20 to 30 seconds.
Intracavernous (off-label route): Using a 100 to 500 mcg/mL concentration, administer laterally (3 or 9 o'clock position) near the base of the penile shaft with small needles (eg, 27-gauge). May consider penile block with local anesthetic prior to administration (Ref).
Vesicant; ensure proper needle or catheter placement prior to and during infusion; avoid extravasation.
Extravasation management: If extravasation occurs, stop infusion immediately; leave cannula/needle in place temporarily but do NOT flush the line; gently aspirate extravasated solution, then remove needle/cannula; elevate extremity; apply dry warm compresses; initiate phentolamine (or alternative antidote) (Ref).
Phentolamine: SUBQ: Dilute 5 to 10 mg in 10 mL NS and administer into extravasation site as soon as possible after extravasation; if IV catheter remains in place, administer initial dose IV through the infiltrated catheter; may repeat in 60 minutes if patient remains symptomatic (Ref).
Alternative to phentolamine: Nitroglycerin topical 2% ointment: Apply a 1-inch strip to the site of ischemia to cover the affected area; may repeat every 8 hours as necessary (Ref).
Oral: OTC products: Administer without regard to food. Administer liquid formulation using an accurate measuring device; do not use household tablespoon.
Parenteral:
IV bolus: 10 mg/mL solution must be diluted prior to administration; a 100 mcg/mL (0.1 mg/mL) ready-to-use formulation requiring no further dilution is also available for IV bolus administration. Administer dose over 20 to 30 seconds (Ref).
Continuous IV infusion: 10 mg/mL solution must be diluted prior to administration. Administer as a continuous infusion via an infusion pump. Central line administration is preferred; extravasation may cause severe ischemic necrosis. If central line is not available, may consider administering for a short duration through a peripheral IV catheter placed in a large vein or via intraosseous access using a more dilute solution or with a second carrier fluid (Ref). Administration into an umbilical arterial catheter is not recommended. Frequent monitoring of the IV catheter site is recommended to rapidly identify extravasation. Refer to institutional policies and procedures; catheter placement/size and vasopressor concentration may vary depending on institution.
Vesicant; ensure proper needle or catheter placement prior to and during infusion; avoid extravasation. If extravasation occurs, stop infusion immediately; leave cannula/needle in place temporarily but do NOT flush the line; gently aspirate extravasated solution, then remove needle/cannula unless needed for IV antidote; elevate extremity; apply dry, warm compresses. Initiate phentolamine (or alternative antidote) (Ref).
IV infusion: 10 mg in 500 mL (concentration: 20 mcg/mL) of D5W or NS, 50 mg in 500 mL (concentration: 100 mcg/mL) of NS, 100 mg in 500 mL (concentration: 200 mcg/mL) of NS, or 100 mg in 250 mL (concentration: 400 mcg/mL) of NS.
Other institutions may use concentrations of 40 mcg/mL or 160 mcg/mL; however, stability information is not available for these concentrations.
IV infusion: 20 mcg/mL, 40 mcg/mL, 60 mcg/mL, 80 mcg/mL, or 400 mcg/mL.
Hypotension or shock: Treatment of severe hypotension or shock that persists during and after adequate fluid volume replacement.
Hypotension during anesthesia: Treatment of vasodilation and hypotension during anesthesia.
Nasal congestion [OTC]: For the temporary relief of nasal congestion due to the common cold, sinusitis, hay fever, or upper respiratory allergies.
Priapism, acute ischemic
Sudafed PE may be confused with Sudafed.
Vazculep may be confused with Bloxiverz (neostigmine) due to similar packaging.
The Institute for Safe Medication Practices (ISMP) includes this medication among its list of drug classes (adrenergic agonist, IV; pediatric liquid medications requiring measurement) which have a heightened risk of causing significant patient harm when used in error (High-Alert Medications in Acute Care Settings).
Biorphen: Brand name for phenylephrine systemic [US] but is also the brand name for orphenadrine [Great Britain]
Neo (Neo-Synephrine, a well-known but DSC brand of phenylephrine) is an error-prone stemmed/coined drug name (mistaken as neostigmine)
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Acetaminophen: May increase serum concentration of Phenylephrine (Systemic). Risk C: Monitor
Alpha1-Blockers: May decrease vasoconstricting effects of Phenylephrine (Systemic). Risk C: Monitor
Atomoxetine: May increase hypertensive effects of Sympathomimetics. Atomoxetine may increase tachycardic effects of Sympathomimetics. Risk C: Monitor
Atropine (Systemic): May increase hypertensive effects of Alpha1-Agonists. Risk C: Monitor
Benzylpenicilloyl Polylysine: Coadministration of Alpha1-Agonists and Benzylpenicilloyl Polylysine may alter diagnostic results. Management: Consider delaying skin testing until alpha1-agonists are no longer required, or use of a histamine skin test as a positive control to assess a patient's ability to mount a wheal and flare response. Risk D: Consider Therapy Modification
Bornaprine: Sympathomimetics may increase anticholinergic effects of Bornaprine. Risk C: Monitor
Bromocriptine: May increase hypertensive effects of Alpha1-Agonists. Management: Consider alternatives to this combination when possible. If combined, monitor for hypertension and tachycardia, and do not coadminister these agents for more than 10 days. Risk D: Consider Therapy Modification
Cannabinoid-Containing Products: May increase tachycardic effects of Sympathomimetics. Risk C: Monitor
Chloroprocaine (Systemic): May increase hypotensive effects of Phenylephrine (Systemic). Risk C: Monitor
CloZAPine: May decrease therapeutic effects of Phenylephrine (Systemic). Risk C: Monitor
Cocaine (Topical): May increase hypertensive effects of Sympathomimetics. Management: Consider alternatives to use of this combination when possible. Monitor closely for substantially increased blood pressure or heart rate and for any evidence of myocardial ischemia with concurrent use. Risk D: Consider Therapy Modification
Dihydralazine: Sympathomimetics may decrease therapeutic effects of Dihydralazine. Risk C: Monitor
Doxofylline: Sympathomimetics may increase adverse/toxic effects of Doxofylline. Risk C: Monitor
Ergot Derivatives (Vasoconstrictive CYP3A4 Substrates): May increase vasoconstricting effects of Alpha1-Agonists. Risk X: Avoid
Esketamine (Injection): May increase adverse/toxic effects of Sympathomimetics. Specifically, the risk for elevated heart rate, hypertension, and arrhythmias may be increased. Risk C: Monitor
FentaNYL: Decongestants may decrease serum concentration of FentaNYL. Risk C: Monitor
Guanethidine: May increase hypertensive effects of Sympathomimetics. Guanethidine may increase arrhythmogenic effects of Sympathomimetics. Risk C: Monitor
Hyaluronidase: May increase vasoconstricting effects of Phenylephrine (Systemic). Management: Do not use hyaluronidase to enhance the dispersion or absorption of phenylephrine. Use of hyaluronidase for other purposes in patients receiving phenylephrine may be considered as clinically indicated. Risk D: Consider Therapy Modification
Iobenguane Radiopharmaceutical Products: Alpha1-Agonists may decrease therapeutic effects of Iobenguane Radiopharmaceutical Products. Management: Discontinue all drugs that may inhibit or interfere with catecholamine transport or uptake for at least 5 biological half-lives before iobenguane administration. Do not administer these drugs until at least 7 days after each iobenguane dose. Risk X: Avoid
Kratom: May increase adverse/toxic effects of Sympathomimetics. Risk X: Avoid
Landiolol: Sympathomimetics may decrease therapeutic effects of Landiolol. Risk C: Monitor
Levothyroxine: May increase therapeutic effects of Sympathomimetics. Sympathomimetics may increase therapeutic effects of Levothyroxine. Levothyroxine may increase adverse/toxic effects of Sympathomimetics. Specifically, the risk of coronary insufficiency may be increased in patients with coronary artery disease. Risk C: Monitor
Linezolid: May increase hypertensive effects of Sympathomimetics. Management: Consider initial dose reductions of sympathomimetic agents, and closely monitor for enhanced blood pressure elevations, in patients receiving linezolid. Risk D: Consider Therapy Modification
Lisuride: May increase hypertensive effects of Alpha1-Agonists. Risk X: Avoid
Melperone: May decrease therapeutic effects of Phenylephrine (Systemic). Risk C: Monitor
Metergoline: May increase adverse/toxic effects of Alpha1-Agonists. Risk C: Monitor
Monoamine Oxidase Inhibitors: May increase hypertensive effects of Alpha1-Agonists. While linezolid is expected to interact via this mechanism, management recommendations differ from other monoamine oxidase inhibitors. Refer to linezolid specific monographs for details. Risk X: Avoid
Pergolide: May increase hypertensive effects of Alpha1-Agonists. Risk C: Monitor
Propacetamol: May increase serum concentration of Phenylephrine (Systemic). Management: Monitor patients closely for increased side effects of phenylephrine if propacetamol is used concomitantly. Patients with underlying blood pressure issues or arrhythmias may need closer monitoring and may warrant consideration of alternative therapies. Risk C: Monitor
Solriamfetol: Sympathomimetics may increase hypertensive effects of Solriamfetol. Sympathomimetics may increase tachycardic effects of Solriamfetol. Risk C: Monitor
Sympathomimetics: May increase adverse/toxic effects of Sympathomimetics. Risk C: Monitor
Tedizolid: May increase adverse/toxic effects of Sympathomimetics. Specifically, the risk for increased blood pressure and heart rate may be increased. Risk C: Monitor
Tricyclic Antidepressants: May increase therapeutic effects of Alpha1-Agonists. Tricyclic Antidepressants may decrease therapeutic effects of Alpha1-Agonists. Risk C: Monitor
Phenylephrine crosses the placenta (Ngan Kee 2009).
Outcome data are available following maternal use of phenylephrine as a decongestant (route of administration not always noted) (Aselton 1985; Heinonen 1977; Rothman 1979; Yau 2013) or for hypotension during cesarean delivery (Fitzgerald 2020; Heesen 2014; Singh 2020; Xu 2018).
Phenylephrine is available over the counter for the symptomatic relief of nasal congestion. Decongestants are not the preferred agents for the treatment of rhinitis during pregnancy. Oral phenylephrine should be avoided during the first trimester of pregnancy due to the potential for adverse pregnancy outcomes (AAAAI/ACAAI [Dykewicz 2020]).
Untreated hypotension associated with spinal anesthesia during cesarean delivery may lead to maternal nausea, vomiting, and fetal acidosis (van Dyk 2022). Phenylephrine injection is recommended for the prevention and/or treatment of maternal hypotension associated with spinal anesthesia in patients undergoing cesarean delivery (ASA 2016; Kinsella 2018; Macones 2019; van Dyk 2022).
It is not known if phenylephrine is present in breast milk.
According to the manufacturer, the decision to breastfeed should consider the risk of infant exposure, the benefits of breastfeeding to the infant, and benefits of treatment to the mother.
Some products may contain phenylalanine and/or sodium.
BP (or mean arterial pressure), heart rate, cardiac output (as appropriate); intravascular volume status; creatinine and urine output; peripheral perfusion; monitor site of infusion for blanching/extravasation.
Consult individual institutional policies and procedures.
Potent, direct-acting alpha-adrenergic agonist with virtually no beta-adrenergic activity; produces systemic arterial vasoconstriction. Such increases in systemic vascular resistance may result in dose-dependent increases in systolic and diastolic blood pressure and reductions in heart rate and cardiac output (most noticeable in patients with preexisting cardiac dysfunction).
Onset of action:
Blood pressure increase/vasoconstriction: IM, SubQ: 10 to 15 minutes; IV: Immediate
Nasal decongestant: Oral: 15 to 30 minutes (Kollar 2007)
Duration:
Blood pressure increase/vasoconstriction: IM: 1 to 2 hours; IV: ~15 to 20 minutes; SubQ: 50 minutes
Nasal decongestant: Oral: ≤4 hours (Kollar 2007)
Absorption: Oral: Erratic and incomplete (Kanfer 1993)
Distribution: Vd: Initial: 26 to 61 L; Vdss: 184 to 543 L (mean: 340 L) (Hengstmann 1982)
Metabolism: Hepatic via oxidative deamination (Oral: 24%; IV: 50%); Undergoes sulfation (Oral [mostly within gut wall]: 46%; IV: 8%) and some glucuronidation; forms inactive metabolites (Kanfer 1993)
Bioavailability: Oral: ≤38% (Hengstmann 1982; Kanfer 1993)
Half-life elimination: Alpha phase: ~5 minutes; Terminal phase: 2 to 3 hours (Hengstmann 1982; Kanfer 1993)
Time to peak: Oral: 0.75 to 2 hours (Kanfer 1993)
Excretion: Urine (mostly as inactive metabolites)
