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Vasopressor / Inotrope

Phenylephrine

Pure α1 agonist

Mechanism: Selective α1 vasoconstriction; reflex bradycardia possible.

Calculate dose for your patient

Enter weight (kg or lb). Always verify before administration.

Computed weight
70.0 kg · 154.3 lb
Bolus
70 mcg – 350 mcg
= 0.70–3.50 mL (100 mcg/mL)
Adult: 50–200 mcg IV. Pure α1.

Weight is saved on this device for the next calculator you open.

Full dose calculator
Onset
<1 min
Duration
5–20 min (bolus)
Metabolism
MAO; hepatic.

Dosing

Adult
Bolus 50–200 mcg IV. Infusion: 20–200 mcg/min (or 0.15–0.75 mcg/kg/min).
Pediatric
Bolus 1–5 mcg/kg.

Indications

  • Hypotension (esp. spinal anesthesia, vasodilatory shock with tachycardia)

Contraindications

  • Severe HTN
  • Closed-angle glaucoma

Side Effects

  • Reflex bradycardia
  • Decreased CO in cardiac dysfunction

Clinical Pearls

1First-line for spinal-induced hypotension at C-section.
2Avoid in low-output states — pure afterload increase can drop CO.

References & Further Reading

  1. 1
    Textbook

    Flood P, Rathmell JP, Shafer S. Stoelting's Pharmacology and Physiology in Anesthetic Practice. 5th ed. Philadelphia: Wolters Kluwer; 2015.

  2. 2
    Textbook

    Gropper MA, Miller RD, Cohen NH, et al., eds. Miller's Anesthesia. 9th ed. Philadelphia: Elsevier; 2020.

  3. 3
    Guideline

    Kinsella SM, Carvalho B, Dyer RA, et al. International consensus statement on the management of hypotension with vasopressors during cesarean section under spinal anaesthesia. Anaesthesia. 2018;73(1):71-92.

  4. 4
    Textbook

    Adriano A, Morris R, eds. 2021 CA-1 Tutorial Textbook (15th Ed.). Stanford University Medical Center, Department of Anesthesiology.

Citations are provided to direct further study. Always check the most current edition of guidelines and society recommendations — the information in this chapter is a teaching summary, not primary source material.