α1 agonist
Phenylephrine
Neo-Synephrine, Biorphen Vasopressor — violet ⚠ 100 mcg/mL (prepared — confirm local)
Pure vasoconstrictor for low BP with a normal or fast heart rate.
Typical adult doses
| Indication | Dose | Onset | Duration |
|---|---|---|---|
| Bolus | 50–100 mcg IV (label 40–100 mcg; max 200 mcg single dose) | Immediate | ≈10–20 min |
| Infusion | 10–35 mcg/min initial (label; max 200 mcg/min) | — | — |
Mechanism
α1-adrenergic agonist → arteriolar vasoconstriction → ↑SVR.
Key effects
- ↑ BP
- Reflex bradycardia
Watch out for
- Bradycardia; ↓ cardiac output in poor ventricles
- Diluted concentrations are prepared locally — read the label
Pimp questions
Pimp question
Why does phenylephrine slow the heart?
Answer
Baroreceptor reflex response to the rise in blood pressure.