Phenylephrine Dosing
For intravenous phenylephrine in adults, start with 0.5-2.0 mcg/kg/min (35-140 mcg/min in a 70-kg adult) for severe hypotension, or use bolus doses of 50-250 mcg for perioperative hypotension. 1, 2
Intravenous Dosing (Adults)
For Severe Hypotension/Vasodilatory Shock
- Continuous infusion: 0.5-2.0 mcg/kg/min (in a 70-kg adult: 35-140 mcg/min) 1
- Septic/vasodilatory shock: 0.5-6 mcg/kg/min titrated to blood pressure goal (doses above 6 mcg/kg/min show no significant incremental benefit) 2
- Preparation: Dilute 10 mg (1 mL of 10 mg/mL) in 500 mL of D5W or normal saline to yield 20 mcg/mL 2
- Administration: Must be diluted before use; central line preferred to avoid tissue necrosis from extravasation 1
For Perioperative Hypotension
- Bolus: 50-250 mcg IV 2
- Continuous infusion: 0.5-1.4 mcg/kg/min titrated to effect 2
- Preparation for bolus: Dilute 10 mg in 99 mL of D5W or normal saline to yield 100 mcg/mL 2
Critical caveat: Phenylephrine is used for severe hypotension (systolic BP <70 mmHg) with low total peripheral resistance. It's relatively contraindicated in hypovolemia—correct volume status first. 1
Intranasal Dosing (Children)
For reducing bleeding during nasotracheal intubation or sinus surgery: 0.1 mL/kg of 0.25-0.5% phenylephrine solution 3
- 0.5% solution was more effective than saline in reducing bleeding (11/27 vs 17/25 patients) 3
- Onset: Peak plasma levels occur at 14±7 minutes 3
- Safety: Causes mild, clinically insignificant blood pressure increases (8% systolic, 14% mean) with highly variable absorption 3
Oral Dosing - NOT RECOMMENDED
Oral phenylephrine is ineffective for nasal congestion and should not be used. 4, 5, 6
- Multiple high-quality studies demonstrate oral phenylephrine at FDA-approved doses (10-40 mg) is no better than placebo for relieving nasal congestion in adults with seasonal allergic rhinitis 4, 6
- The FDA has proposed removing oral phenylephrine from over-the-counter products due to lack of efficacy 5
- Pediatric data: Limited pharmacokinetic studies show absorption occurs, but no efficacy data support its use in children 7, 5
Pediatric IV Dosing - Limited Data
No established pediatric IV dosing guidelines exist in the provided evidence. The anaphylaxis guidelines focus on epinephrine, not phenylephrine, for pediatric emergencies. One small pilot study explored 5 mcg/kg IV as a test dose during epidural placement, showing a 25% decrease in heart rate at 1 minute, but this was not validated for therapeutic use 8.
Key Safety Considerations
- Extravasation: Can cause tissue necrosis. If it occurs, infiltrate 5-10 mg phentolamine diluted in 10-15 mL saline into the site immediately 1
- Monitoring: Continuous hemodynamic monitoring is essential during infusion 1, 2
- Contraindications: Hypersensitivity to phenylephrine or sulfites (IV formulation contains sulfites) 2
- Drug interactions: Potentiated by MAOIs, β-blockers, tricyclic antidepressants; antagonized by α-blockers 2
- Volume status: Correct intravascular volume depletion and acidosis before administration, as acidosis reduces effectiveness 2