Phenylephrine
Common Brand Names: Generic
Therapeutic Class: Alpha/Beta agonist
Common Injectable Dosage Forms:
Solution for Injection: 10 mg/mL (1 mL, 5 mL)
Dosage Ranges:
Hypotension/Shock:
Children: IV bolus of 5-20 mcg/kg/dose every 10-15 minutes as needed. IV infusion of 0.1-0.5 mcg/kg/minute.
Adults: IV bolus of 0.1-0.5 mg/dose every 10-15 minutes as needed. IV infusion initial dose is 100-180 mcg/minute. When BP is stabilized, use a maintenance dose of 40-60 mcg/minute. Total dosing range of 0.4-9.1 mcg/kg/minute has been used.
Paroxysmal supraventricular tachycardia:
Children: IV dose 5-10 mcg/kg/dose over 20-30 seconds.
Adults: IV 0.25-0.5 mg/dose over 20-30 seconds.
Administration and Stability: Phenylephrine may cause necrosis if extravasation occurs during IV administration or SubQ administration. Use phentolamine as antidote. Store vials at room temperature, protected from light. Dilute IV infusion of 10 mg in 500 mL NS or D5W. IV injection vials should be diluted with Sterile Water for Injection (SWFI) to a concentration of 1 mg/mL.
Pharmacology/Pharmacokinetics: Phenylephrine is a potent, direct acting alpha-adrenergic stimulator with weak beta-adrenergic activity. It causes- vasoconstriction of the arterioles and produces systemic arterial vasoconstriction. Onset of action by IM or SubQ route is 10-15 minutes. Onset of action by IV route is immediate. Duration of effect is 15 minutes to 2 hours.
Drug and Lab Interactions: When taken with sympathomimetics, phenylephrine may induce tachycardia or arrhythmias. Phenylephrine may increase the effects of monoamine oxidase inhibitors. Nonselective beta-blockers may increase hypertensive effects. Avoid use with tricyclic antidepressants and methyldopa.
Contraindications/Precautions: Contraindicated in patients with hypersensitivity to phenylephrine as well as patients with hypertension and ventricular tachycardia. Use with caution in the elderly, patients with hyperthyroidism, bradycardia, myocardial disease, or severe CAD. Pregnancy Category C.
Monitoring Parameters: Blood pressure, pulse, excitability, irritability, and anxiety
Adverse Effects: Reflex bradycardia, excitability, arrhythmia, hypertension, headache, and respiratory distress have all been reported.
Common Clinical Applications: Used in the treatment of hypotension and vascular failure in shock.
