Phenylephrine (Neosynephrine)


Name: Phenylephrine (NeosynephrineR)
Classification: sympathomimetic, vasopressor
  • stimulates alpha adrenergic receptors resulting in
    • vasoconstriction
    • decreased heart rate 
    • increased peripheral resistance
  • used to increase blood pressure
  • Bolus dose
    • hypotension or shock:  0.1-0.5mg as slow IV direct injection q10-15min (or 1-10mg IM/SC q1-2hours)
    • PSVT:  0.5-1mg as rapid direct IV injection q60-90 seconds
  • IV infusion: 
    • 0.04-0.18mg/min (40-180 mcg/min), titrated to effect 
Administration: IV Infusion:
100 mg/250ml dextrose 5% or normal saline 0.9%
  • hypovolemia, hypoxemia and acidosis should be corrected concurrently with initiation of therapy
  • should be weaned off
Adverse Effects:
  • bradycardia 
  • arrhythmias
  • increased myocardial oxygen consumption; avoid in patients with left ventricular dysfunction
  • peripheral or mesenteric ischemia
  • acute kidney injury
  • headache
  • restlessness or excitability
  • extravasation of drug will cause tissue necrosis and ulceration (treat with 5-15mg phentolamine in NS - see phentolamine monograph)
Drug Interactions:
  • phenylephrine + atropine = increased BP and tachycardia
  • phenylephrine + halogenated anaesthetics = increased cardiac irritability
  • phenylephrine + alpha blocking agents = blockade of vasopressor effect
  • phenylphrine + other sympathomimetics = increased risk of toxicity
Monitoring Therapy:
  • IV site
  • blood pressure
  • heart rate and ECG rhythm
  • urine output
  • urea, creatinine
  • central or mixed venous oxygen saturation
  • lactate
  • cardiac index if monitored
  • SVRI if monitored
  • lactate
  • changes in skin colour or tempurature
  • chest pain
Adult Critical Care Protocol:
  • May be administered IV direct or by IV infusion by a nurse in Adult Critical Care.
  • May be titrated by a nurse in Adult Critical Care.
  • Must be administered via central venous access device; in emergency situations may be temporarily infused through a peripheral vasuclar access device until a central venous line can be established.
  • Patient requires placement of an arterial line to monitor BP.
  • Continuous infusions must be administered by infusion device and the pump library must be enabled.
  • Should not be infused via the proximal injectate port (blue) of a pulmonary artery catheter. If this is the only available central venous line, it may be administered through the proximal injectate port but thermodilution cardiac output measurements must not be measured during infusion).

Lynne Kelly, Pharmacist, CCTC
Brenda Morgan, Clinical Nurse Specialist, CCTC
Last Update: September 20, 2018

Reviewed: January 12, 2017

Revised: March 3, 2017, updated September 17, 2018