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# Norepinephrine
## Overview
Norepinephrine is a vasopressor and inotropic agent that acts primarily on alpha-1 adrenergic receptors, causing vasoconstriction and increasing systemic vascular resistance. It also has some beta-1 adrenergic receptor activity, leading to increased heart rate and contractility.
## Primary Indications
* Management of severe hypotension unresponsive to adequate fluid resuscitation.
* Septic shock.
* Cardiogenic shock.
## Adult Dosing
* **Starting Dose:** 0.01 to 0.02 mcg/kg/min IV.
* **Titration:** Titrate upward in increments of 0.01 to 0.02 mcg/kg/min every 5 to 10 minutes until the desired blood pressure is achieved.
* **Maximum Dose:** Typically 0.3 mcg/kg/min IV, though higher doses may be used in specific refractory cases under close monitoring.
## Pediatric Dosing
* **Starting Dose:** 0.05 to 0.1 mcg/kg/min IV.
* **Titration:** Titrate to desired hemodynamic effect, usually increasing by 0.05 to 0.2 mcg/kg/min every 10-15 minutes.
* **Maximum Dose:** Generally 1 mcg/kg/min IV, but higher doses may be used cautiously. Specific protocols may vary.
## Dose Adjustments
* No specific dose adjustments are typically needed for hepatic or renal impairment. Dosing is primarily guided by hemodynamic response and patient tolerance.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during cyclopropane and halogenated hydrocarbon anesthesia (may cause severe hypertension and cardiac arrhythmias).
* Severe peripheral or mesenteric vascular thrombosis (risk of increasing ischemia).
## Adverse Effects
* **Cardiovascular:** Hypertensive crisis, bradycardia, arrhythmias (tachycardia, ventricular extrasystoles), peripheral ischemia, gangrene (especially in extremities).
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Other:** Extravasation can cause tissue necrosis; infiltration may require phentolamine injection.
## Key Drug Interactions
* **MAO Inhibitors & Tricyclic Antidepressants:** May potentiate the pressor response; concurrent use is generally contraindicated or requires extreme caution and dose reduction.
* **Beta-blockers:** May blunt the beta-1 effects of norepinephrine, leading to unopposed alpha-1 vasoconstriction and potentially severe hypertension.
* **Alpha-blockers:** May antagonize the pressor effects.
* **Oxytocics:** May cause severe persistent hypertension.
* **Ergot alkaloids:** May potentiate the pressor effect and cause vasoconstriction.
## Monitoring
* Continuous blood pressure monitoring (arterial line preferred).
* Heart rate and rhythm.
* Central venous pressure (CVP) and/or pulmonary artery catheter (PAC) readings if indicated.
* Urine output.
* Extremity perfusion and signs of ischemia.
* Infusion site for signs of extravasation.
## Clinical Pearls
* Always dilute norepinephrine in a compatible IV fluid before administration (e.g., 5% dextrose in water, 0.9% sodium chloride). Consult pharmacy for recommended concentrations and compatibilities.
* Administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, stop the infusion, aspirate residual drug, and infiltrate the affected area with phentolamine.
* Norepinephrine is light-sensitive; protect infusions from light.
* Titrate to the lowest effective dose to achieve the target mean arterial pressure (MAP), typically 65 mmHg, or as per local protocol.
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**Disclaimer:** This information is intended for healthcare professionals. It is essential to consult the official prescribing information and institutional protocols for complete and up-to-date guidance. Dosing and management may vary based on patient-specific factors and clinical context. Always verify current prescribing information before use.
