Phenylephrine

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General

  • Type: Vasopressors
  • Dosage Forms:
  • Common Trade Names: Neosynephrine

Adult Dosing

Hypotension

  • Start 100-200 mcg/min then taper down
    • 40-60 mcg/min works for most

Low Flow Priapism

  • Dilute phenylephrine 1mg in 9mL NS for final concentration of 100mcg/mL
    • For 500 mcg/ml, take 0.5 ml of 10mg/ml phenylephrine, and dilute in 9.5 cc NS
  • Inject base of penis with 29-Ga needle (after blood aspiration to confirm position)
    • 100-500 mcg every 3-5min (max 1000 mcg) until resolution or 1 hour

Pediatric Dosing

Special Populations

  • Pregnancy Rating: C
  • Lactation: infant risk cannot be ruled out
  • Renal Dosing
    • Adult
    • Pediatric
  • Hepatic Dosing
    • Adult
    • Pediatric

Contraindications

  • Allergy to class/drug

Adverse Reactions

  • Baroreceptor-mediated reflex bradycardia
  • If extravasates use phentolamine

Serious

Common

Pharmacology

  • Half-life:
  • Metabolism:
  • Excretion:
  • Mechanism of Action: selective α1 agonist causes vasoconstriction

Primary Receptor

  • α1

Relative Effects

  • ↑SVR
  • ↓HR (reflex bradycardia)

Notes

  • Use with caution in patients with spinal cord injury-related bradycardia
  • Useful for treatment of vasodilatory shock when norepinephrine or dopamine have precipitated tachyarrhythmias
  • In patients with ↓LV function, unopposed α1 may lead to decreased CO or myocardial ischemia
    • However clinical trials do not support these effects when used in clinically appropriate dose range

Indication

  • Neurogenic Shock
  • Second line agent for septic shock

See Also

http://www.atsjournals.org/doi/abs/10.1164/rccm.201006-0972CI?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed#readcube-epdf

References