Phenylephrine
Synthetic α1-agonist
Pure α1 agonist → vasoconstriction. No β activity.
Indications
- •Anesthesia-induced hypotension
- •OB spinal hypotension (preferred over ephedrine for fetal pH)
- •Mydriasis (ophthalmic)
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Bolus | 50–200 mcg IV | — |
| Infusion | 0.15–1.5 mcg/kg/min | — |
| OB spinal prophylaxis | 0.5–1 mcg/kg/min infusion at spinal placement | — |
Pharmacokinetics
Onset 1 min. Duration 10–20 min.
Hemodynamic effects
↑SVR, ↑BP. Reflex bradycardia (often ↓CO).
Side effects
- !Bradycardia + ↓CO (relevant in poor LV function)
- !Reduced uteroplacental flow at high dose
Contraindications
- ×Severe LV dysfunction (relative — reduced CO with vasoconstriction)
Clinical pearls
- ★OB spinal: phenylephrine maintains umbilical artery pH better than ephedrine.
- ★Cardiac surgery off-pump: phenyl preferred for systemic pressure during graft anastomoses.
- ★Watch for reflex bradycardia in LVH/HOCM patients.
Education only — confirm against current package inserts and institutional protocols. Doses assume normal organ function unless otherwise noted.