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# Norepinephrine
## Overview
Norepinephrine is a sympathomimetic amine that acts as a vasopressor and inotrope. It primarily stimulates alpha-1 adrenergic receptors, leading to vasoconstriction and increased peripheral vascular resistance. It also has some beta-1 adrenergic receptor activity, increasing heart rate and contractility.
## Primary Indications
* Treatment of hypotension and shock, particularly septic shock and cardiogenic shock.
* Restoration and maintenance of blood pressure during cardiac arrest.
## Adult Dosing
* **Hypotension/Shock:** Typically initiated at 0.01 to 0.02 mcg/kg/min IV, titrated to achieve target mean arterial pressure (MAP), often 65 mmHg or higher. Usual maintenance doses range from 0.01 to 0.3 mcg/kg/min IV. Higher doses may be required in severe shock.
* **Cardiac Arrest:** 1 mg IV/IO every 3-5 minutes, as per ACLS guidelines.
## Pediatric Dosing
* **Hypotension/Shock:** Dosing is highly variable and often guided by institutional protocols. A common starting dose is 0.05 mcg/kg/min IV, titrated upwards as needed.
* **Cardiac Arrest:** 0.01 mg/kg IV/IO (10 mcg/kg) every 3-5 minutes, as per PALS guidelines.
## Dose Adjustments
* No specific dose adjustments are generally required for hepatic or renal impairment, as the drug is metabolized by enzymes in the liver and removed by the kidneys, but efficacy and toxicity should be closely monitored.
## Contraindications
* Hypersensitivity to norepinephrine.
* Generally contraindicated in patients with **tylenol overdose** treated with intravenous N-acetylcysteine unless other vasopressors are ineffective.
## Adverse Effects
* Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, tissue necrosis (with extravasation), anxiety, headache, dizziness, dyspnea, decreased cardiac output (at high doses), and reduced splanchnic blood flow.
## Key Drug Interactions
* **MAO Inhibitors and Tricyclic Antidepressants:** Can potentiate the pressor effects of norepinephrine, potentially leading to hypertensive crisis. Discontinue MAOIs at least 14 days prior to norepinephrine initiation.
* **Beta-Blockers:** Can lead to unopposed alpha-adrenergic stimulation, causing severe hypertension.
* **Alpha-Blockers:** Can reduce the pressor effects.
* **Oxytocic agents:** May cause severe, sustained hypertension.
* **Guanethidine:** May enhance the pressor effect.
## Monitoring
* Continuous blood pressure monitoring (arterial line preferred).
* Heart rate and rhythm.
* Central venous pressure (if available).
* Urine output.
* Circulation to extremities (assess for signs of ischemia).
* Infusion site for signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately and administer phentolamine infiltrated locally into the affected area.
* Norepinephrine is light-sensitive; protect infusion bags and tubing from light.
* Titrate to the lowest effective dose to achieve target MAP and minimize adverse effects.
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*This information is intended for clinical use and does not replace comprehensive drug reference materials. Always consult current prescribing information and institutional protocols before use.*
