Phenylephrine (Neo-Synephrine)

Category:

• Nervous system

Description:

• Vasopressor

Indications:

• Hypotension, shock, paroxysmal supraventricular tachycardia (PSVT)

• Prolongation of spinal anesthesia, vasoconstriction in regional anesthesia

Contraindications:

• Ventricular fibrillation/tachycardia, pheochromocytoma,

• Narrow-angle glaucoma, severe hypertension

Precautions:

• Pregnancy category C

• Arterial embolism, peripheral vascular disease, elderly, hyperthyroidism

• bradycardia, myocardial disease, severe arteriosclerosis

Adverse Reactions (Side Effects):

• CNS: anxiety, dizziness, headache, insomnia, tremor

• CV: angina, ectopic beats, hypertension, palpitations, reflex bradycardia, tachycardia

• GI: nausea, vomiting

• SKIN: gangrene, necrosis, tissue sloughing with extravasation  

Dosage:

Administered intravenously, intramuscularly, subcutaneously

• Adult:            

  • Hypotension: 

    • SC/IM 2-5mg, may repeat every 10-15 minutes if needed

    • IV 0.1-0.5mg, may repeat every 10-15 minutes if needed

    • IV INF 10mg/500ml D5W given 100-180 drops/minute (based on 20 drops/ml), then 40-60 drops/minute titrated to blood pressure

  • PSVT: 

    • IV bolus 0.5mg given rapidly; subsequent doses should not exceed previous dose by >0.1-0.2mg; max single dose 1mg

  • Prolongation of spinal anesthesia: 

    • Add 2-5mg to anesthetic solution; increases duration of block by 50%

  • Prevention of hypotension in spinal anesthesia: 

    • SC/IM 2-3mg 3-4 minutes before anesthetic injection

  • Vasoconstriction in regional anesthesia: 

    • Add 1mg to 20ml anesthetic solution

• Child:            

  • Hypotension: 

    • SC/IM 0.1 mg/kg/dose every 1-2 hours (max 5mg)

    • IV bolus 2-50 mcg/kg/dose every 10-15 minutes

    • IV INF 0.1-0.5 mcg/kg/min

  • PSVT:

    •  IV 5-10 mcg/kg/dose over 20-30 seconds

  • Prevention of hypotension in spinal anesthesia: 

    • SC/IM 0.05-0.1 mg/kg/dose