phenylephrine hydrochloride
Nasal
4-Way Fast Acting, Afrin Children’s Pump Mist, Little Noses Gentle Formula, Neo-Synephrine, Nostril, Rhinall, Vicks Sinex

Oral
AH-chew D, Little Colds for Infants and Children

Parenteral
Neo-Synephrine

Ophthalmic
AK-Dilate, AK-Nefron, Dionephrine ◆, Mydfrin 2.5%, Neo-Synephrine, Phenoptic, Prefrin Liquifilm, Relief

Available forms
Available by prescription only
Injection: 10 mg/ml parenteral
Ophthalmic solution: 2.5%, 10%
Tablets (chewable): 10 mg
Available without a prescription
Nasal solution: 0.125%, 0.25%, 0.5%, 1%
Nasal spray: 0.25%, 0.5%, 1%
Ophthalmic solution: 0.12%
Oral solution: 0.25%

Indications and dosages
 Hypotensive emergencies during spinal anesthesia. Adults: Initially, 0.1 to 0.2 mg I.V.; subsequent doses should also be low (0.1 mg).
 Prevention of hypotension during spinal or inhalation anesthesia. Adults: 2 to 3 mg S.C. or I.M. 3 to 4 minutes before anesthesia.
 Mild to moderate hypotension. Adults: 1 to 10 mg S.C. or I.M. (initial dose shouldn’t exceed 5 mg). Additional doses may be given in 1 to 2 hours if needed. Or 0.1 to 0.5 mg slow I.V. injection (initial dose shouldn’t exceed 0.5 mg). Additional doses may be given q 10 to 15 minutes.
Children: 0.1 mg/kg or 3 mg/m² I.M. or S.C.
 Paroxysmal supraventricular tachycardia. Adults: Initially, 0.5 mg rapid I.V.; subsequent doses may be increased in increments of 0.1 to 0.2 mg. Maximum dose shouldn’t exceed 1 mg.
 Prolongation of spinal anesthesia. Adults: 2 to 5 mg added to anesthetic solution.
 Adjunct in the treatment of severe hypotension or shock. Adults: 0.1 to 0.18 mg/minute I.V. infusion. After blood pressure stabilizes, maintain at 0.04 to 0.06 mg/minute, adjusted to patient response.
 Vasoconstrictor for regional anesthesia. Adults: 1 mg phenylephrine added to 20 ml local anesthetic.
 Mydriasis (without cycloplegia). Adults: Instill 1 or 2 drops 2.5% or 10% solution in eye before procedure. May be repeated in 10 to 60 minutes if needed.
 Posterior synechia (adhesion of iris). Adults: Instill 1 drop of 10% solution in eye three or more times daily with atropine sulfate.
 Diagnosis of Horner’s or Raeder’s syndrome. Adults: Instill a 1% or 10% solution in both eyes.
 Initial treatment of postoperative malignant glaucoma. Adults: Instill 1 drop of a 10% solution with 1 drop of a 1% to 4% atropine sulfate solution three or more times daily.
 Nasal, eustachian tube, or sinus ◇ congestion. Adults and children older than age 12: Apply 2 to 3 drops or sprays of 0.25% to 1% solution instilled in each nostril q 4 hours; or 10 to 20 mg P.O. tablets q 4 hours.
Children ages 6 to 12: Apply 2 to 3 drops or sprays of 0.25% solution in each nostril; or 10 mg P.O. (tablets) q 4 hours.
Children ages 2 to 6: Apply 2 to 3 drops of 0.125% solution in each nostril q 4 hours; or 1 ml P.O. (oral drops) q 4 hours.
 Conjunctival congestion. Adults: 1 to 2 drops of 0.12% to 0.25% solution applied to conjunctiva q 3 to 4 hours, p.r.n.

Pharmacodynamics
Vasopressor action: Acts predominantly by direct stimulation of alpha-adrenergic receptors, which constrict resistance and capacitance blood vessels, resulting in increased total peripheral resistance; increased systolic and diastolic blood pressure; decreased blood flow to vital organs, skin, and skeletal muscle; and constriction of renal blood vessels, reducing renal blood flow. Main therapeutic effect is vasoconstriction.
 Also may act indirectly by releasing norepinephrine from its storage sites. Doesn’t stimulate beta receptors except in large doses (activates beta₁ receptors). Tachyphylaxis (tolerance) may follow repeated injections.
 Other alpha-adrenergic effects include action on the dilator muscle of the pupil (producing contraction) and local decongestant action in the arterioles of the conjunctiva (producing constriction).
 Acts directly on alpha-adrenergic receptors in the arterioles of conjunctiva nasal mucosa, producing constriction. Vasoconstricting action on skin, mucous membranes, and viscera slows the vascular absorption rate of local anesthetics, which prolongs their action, localizes anesthesia, and decreases the risk of toxicity.
 May cause contraction of pregnant uterus and constriction of uterine blood vessels.

Pharmacokinetics
Absorption: Pressor effects occur rapidly. Nasal or conjunctival decongestant effects last 30 minutes to 4 hours. Peak effects for mydriasis 15 to 60 minutes for 2.5% solution; 10 to 90 minutes for 10% solution. Mydriasis recovery time is 3 hours for 2.5% solution; 3 to 7 hours for 10% solution.
Distribution: No information available.
Metabolism: Metabolized in liver and intestine by MAO.
Excretion: No information available.

Contraindications and precautions
All forms are contraindicated in patients hypersensitive to drug. Injected form is also contraindicated in those with severe hypertension or ventricular tachycardia. Ophthalmic form is also contraindicated in patients with angle-closure glaucoma and in those who wear soft contact lenses.
  Use all forms cautiously in elderly patients and in patients with hyperthyroidism or cardiac disease. Use nasal and ophthalmic forms cautiously in patients with type 1 diabetes mellitus, hypertension, or advanced arteriosclerotic changes and in children who have low body weight. Use injectable form cautiously in patients with severe atherosclerosis, bradycardia, partial heart block, myocardial disease, or allergy to sulfites.

Interactions
Drug-drug. Antihypertensives, diuretics, nitrates: Decreases pressor response (hypotension). Monitor patient closely.
Cardiac glycosides, epinephrine, general anesthetics (cyclopropane, halothane), guanadrel, guanethidine, levodopa, MAO inhibitors, tricyclic antidepressants, other sympathomimetics: Increases risk of arrhythmias, including tachycardia. Monitor patient closely; don’t use with MAO inhibitors.
Cycloplegic antimuscarinics (such as atropine): Increases mydriatic response to phenylephrine. Use together cautiously.
Doxapram, ergot alkaloids, MAO inhibitors, mazindol, methyldopa, oxytocics: Potentiates pressor effects. Monitor patient closely; don’t use with MAO inhibitors.
Levodopa: Decreases mydriatic response to phenylephrine. Use together cautiously.
Nitrates: Reduces antianginal effects. Evaluate response to therapy.
Thyroid hormones: Increases effects of either drug. Monitor patient closely.

Adverse reactions
CNS: headache; excitability (with injected form); brow ache (with ophthalmic form); tremor, dizziness, nervousness (with nasal form).
CV: bradycardia, arrhythmias, hypertension (with injected form); hypertension (with 10% solution), tachycardia, palpitations, PVCs, MI (with ophthalmic form); palpitations, tachycardia, hypertension.
EENT: transient eye burning or stinging on instillation, blurred vision, increased intraocular pressure, keratitis, lacrimation, reactive hyperemia of eye, allergic conjunctivitis, rebound miosis (with ophthalmic form); transient burning or stinging, dryness of nasal mucosa, rebound nasal congestion with continued use (with nasal form).
GI: nausea (with nasal form).
Respiratory: asthmatic episodes.
Skin: pallor (with nasal form), dermatitis (with ophthalmic form), tissue sloughing with extravasation (with injected form), diaphoresis (with ophthalmic form).
Other: tachyphylaxis (may occur with continued use), anaphylaxis, decreased organ perfusion (with prolonged use), trembling.

Effects on lab test results
None reported.

Overdose and treatment
Toxicity may cause exaggeration of common adverse reactions, palpitations, paresthesia, vomiting, arrhythmias, and hypertension.
 Use atropine sulfate to block reflex bradycardia; phentolamine to treat excessive hypertension; and propranolol to treat cardiac arrhythmias, or levodopa to reduce excessive mydriatic effect of ophthalmic preparation as needed.

Special considerations
• Hypovolemic states should be corrected before administration of drug; phenylephrine shouldn’t be used in place of fluid, blood, plasma, and electrolyte replacement.
• Give I.V. through large veins, and monitor flow rate. To treat extravasation ischemia, infiltrate site promptly and liberally with 10 to 15 ml of saline solution containing 5 to 10 mg of phentolamine through fine needle. Topical nitroglycerin has also been used.
• During I.V. administration, monitor pulse, blood pressure, and CVP every 2 to 5 minutes. Control flow rate and dosage to prevent excessive increases. I.V. overdoses can induce ventricular arrhythmias.
• Drug is chemically incompatible with butacaine, sulfate, alkalies, ferric salts, and oxidizing drugs and metals.
Ophthalmic form
• Apply digital pressure to lacrimal sac during and for 1 to 2 minutes after instillation to prevent systemic absorption.
• Prolonged exposure to air or strong light may cause oxidation and discoloration. Don’t use if solution is brown or contains precipitate.
• To prevent contamination, don’t touch applicator tip to any surface. Instruct patient in proper technique.
• Drug may cause false-normal tonometry readings.
Nasal form
• Prolonged or long-term use may result in rebound congestion and chronic swelling of nasal mucosa.
• To reduce risk of rebound congestion, use weakest effective dose.
• After use, rinse tip of spray bottle or dropper with hot water and dry with clean tissue.
Breast-feeding patients
• It isn’t known if drug appears in breast milk. Use cautiously in breast-feeding women.
Pediatric patients
• Infants and children may be more susceptible than adults to drug’s effects. Because of risk of precipitating severe hypertension, only ophthalmic solutions containing 0.5% or less should be used in infants younger than age 1. The 10% ophthalmic solution is contraindicated in infants. Most manufacturers recommend that the 0.5% nasal solution not be used in children younger than age 12 except under medical supervision, and the 0.25% nasal solution shouldn’t be used in children younger than age 6 except under medical supervision.
Geriatric patients
• Effects may be exaggerated in elderly patients. In patients older than age 50, phenylephrine (ophthalmic solution) appears to alter the response of the dilator muscle of the pupil so that rebound miosis may occur the day after drug is given.

Patient education
• Tell patient to store away from heat, light, and humidity (not in bathroom medicine cabinet) and out of children’s reach.
• Warn patient to use only as directed. If using OTC product, patient should follow directions on label and not use more often or in larger doses than prescribed or recommended.
• Caution patient not to exceed recommended dosage regardless of formulation; patient shouldn’t double, decrease, or omit doses nor change dosage intervals unless so instructed.
• Tell patient to call if drug provides no relief in 2 days after using ophthalmic solution or 3 days after using nasal solution.
• Explain that systemic absorption from nasal and conjunctival membranes can occur. Patient should report systemic reactions, such as dizziness and chest pain, and stop drug.
Ophthalmic form
• Instruct patient not to use if solution is brown or contains a precipitate.
• Tell patient to wash hands before applying and to use finger to apply pressure to lacrimal sac during and for 1 to 2 minutes after instillation to decrease systemic absorption.
• Warn patient to avoid touching tip to any surface to prevent contamination.
• Inform patient that after applying drops, pupils will become unusually large. Patient should use sunglasses to protect eyes from sunlight and other bright lights, and call if effects persist 12 hours or longer.
Nasal form
• After use, tell patient to rinse tip of spray bottle or dropper with hot water and dry with clean tissue.
• Instruct patient to blow nose gently (with both nostrils open) to clear nasal passages before using drug.
• Teach patient appropriate method:
- Drops: Tilt head back while sitting or standing up, or lie on bed and hang head over side. Stay in position a few minutes to permit drug to spread through nose.
- Spray: With head upright, squeeze bottle quickly and firmly to produce 1 or 2 sprays into each nostril; wait 3 to 5 minutes, blow nose and repeat dose.
• Tell patient that increased fluid intake helps keep secretions liquid.
• Warn patient to avoid using OTC drugs with phenylephrine to prevent possible hazardous interactions.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use