phenylephrine hydrochloride (NeoSynephrine, Neofrin)

GENERIC NAME: phenylephrine hydrochloride

BRAND NAME: NeoSynephrine, Neofrin

DRUG CLASS AND MECHANISM: Phenylephrine is a man-made drug that stimulates receptors (alpha1 receptors) on blood vessels and cause blood vessels to constrict (vasoconstriction). It is a vasoconstrictor medication, structurally similar to epinephrine and ephedrine. Vasoconstriction increases blood pressure. Phenylephrine increases blood pressure and heart rate without affecting heart rhythm.



PREPARATIONS: Injection: 10 mg/ml

STORAGE: Store phenylephrine injections between 15 C to 30 C (59 to 86 F).

PRESCRIBED FOR: Phenylephrine is used for maintenance of blood pressure during anesthesia, for the treatment of vascular failure in shock or shock-like states, drug-induced hypotension, and to overcome paroxysmal supraventricular tachycardia (abnormally fast heart beats) during anesthesia.



  • Mild to moderate hypotension, hypotension during spinal anesthesia: 0.1 to 0.5 mg intravenously every 10 to 15 minutes or 1 to 5 mg subcutaneously or by intramuscular injection.
  • Severe Hypotension, shock: 100 to 180 mcg/minute continuous intravenous infusion until blood pressure is stable; decrease rate to 40 to 60 mcg/minute to maintain blood pressure.
  • Paroxysmal supraventricular tachycardia: 0.5 mg intravenous injection rapidly given within 20 to 30 seconds. Additional dose should not exceed 0.1 to 0.2 mg more than preceding dose, based on the initial blood pressure response; maximum dose is 1 mg.

DRUG INTERACTIONS: Phenylephrine should be used cautiously with MAO inhibitors like selegiline (Eldepryl, Zelapar), phenelzine (Nardil), isocarboxazid (Marplan), because they can also increase blood pressure and can cause a serious hypertensive episode. A similar reaction occurs when phenylephrine is combined with amphetamine and related drugs.

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