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

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