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# Norepinephrine
## Overview
Norepinephrine is a potent alpha-1 adrenergic agonist and a weaker beta-1 adrenergic agonist. It causes vasoconstriction, leading to increased systemic vascular resistance and blood pressure. It also has a mild positive inotropic effect.
## Primary Indications
* Treatment of hypotension and shock, particularly septic shock and distributive shock.
* Restoration and maintenance of blood pressure.
## Adult Dosing
* **Intravenous Infusion:** Typically initiated at 0.01 to 0.02 mcg/kg/min.
* **Titration:** Titrate infusion rate upward based on patient's hemodynamic response (e.g., mean arterial pressure [MAP] > 65 mmHg).
* **Maximum Dose:** Doses up to 0.3 mcg/kg/min may be required in severe cases. The exact maximum dose may vary based on clinical judgment and local protocols.
## Pediatric Dosing
* **Intravenous Infusion:** Typically initiated at 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate infusion rate upward based on patient's hemodynamic response.
* **Maximum Dose:** Doses up to 1 mcg/kg/min may be required in severe cases. The exact maximum dose may vary based on clinical judgment and local protocols.
## Dose Adjustments
* No specific dose adjustments are typically required for hepatic or renal impairment, as norepinephrine is primarily metabolized in the liver and its active metabolites are excreted renally. However, prolonged use in renal impairment may warrant closer monitoring.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during general anesthesia with cyclopropane or halothane (risk of severe hypertension and arrhythmias).
## Adverse Effects
* **Common:** Hypertension, bradycardia (reflex), peripheral ischemia, extravasation leading to tissue necrosis, headache, anxiety.
* **Serious:** Myocardial infarction, arrhythmias, reduced blood flow to vital organs (e.g., kidneys, brain).
## Key Drug Interactions
* **MAO Inhibitors & Tricyclic Antidepressants:** Can potentiate pressor effects, leading to severe hypertension.
* **Beta-Blockers:** May blunt the desired pressor effects and unopposed alpha-stimulation can lead to severe hypertension.
* **Alpha-Blockers:** May antagonize the vasoconstrictive effects.
* **Ergot Alkaloids:** Can potentiate vasoconstriction.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (arterial line preferred), heart rate.
* **Perfusion:** Urine output, peripheral perfusion (skin color, temperature, capillary refill).
* **Infusion Site:** Frequent checks for signs of extravasation.
* **Cardiac:** ECG for arrhythmias.
* **Electrolytes:** Especially potassium, with prolonged use.
## Clinical Pearls
* Administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion and infiltrate the affected area with phentolamine.
* Norepinephrine can cause reflex bradycardia; use caution in patients with pre-existing bradyarrhythmias.
* The goal is to maintain adequate organ perfusion, not necessarily a specific blood pressure number, though a MAP > 65 mmHg is often targeted.
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*Disclaimer: This information is intended for healthcare professionals. It is crucial to consult the most current prescribing information and relevant clinical guidelines for complete details and to verify dosages and safety recommendations before prescribing.*
