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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 adrenergic receptors (inotropic effect). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Acute hypotensive states (e.g., septic, cardiogenic, or vasodilatory shock).
* Cardiac arrest (less common).
## Adult Dosing
* **Initial Infusion:** 0.01–0.05 mcg/kg/min (or 5–10 mcg/min).
* **Titration:** Titrate by 0.02–0.05 mcg/kg/min every 3–5 minutes based on hemodynamic response to reach target Mean Arterial Pressure (MAP).
* **Maintenance:** Typical range is 0.05–0.5 mcg/kg/min.
* **Maximum:** No formal universal maximum; doses >1.0–3.0 mcg/kg/min are associated with severe peripheral ischemia and refractory shock.
## Pediatric Dosing
* **Continuous Infusion:** 0.05–0.1 mcg/kg/min.
* **Titration:** Titrate to effect in increments of 0.05 mcg/kg/min.
* **Maximum:** Typically 1–2 mcg/kg/min; dosage depends heavily on local institutional protocols and ICU guidelines.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific dosage adjustments established; however, monitor closely for accumulation or hemodynamic variability.
* **Tapering:** Must be tapered slowly to prevent rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary/cerebral perfusion until blood volume replacement is completed).
* Mesenteric or peripheral vascular thrombosis (with caution).
## Adverse Effects
* **Common:** Hypertension, headache, anxiety.
* **Serious:** Tissue necrosis/sloughing upon extravasation, cardiac arrhythmias (tachycardia or bradycardia reflexively), peripheral ischemia (fingers, toes, gut), and myocardial ischemia.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May produce severe, prolonged hypertension.
* **Beta-Blockers:** May decrease the inotropic effects of norepinephrine and lead to unopposed alpha-mediated vasoconstriction.
* **Cyclopropane/Halogenated Hydrocarbons:** Increased risk of ventricular arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous MAP monitoring (preferably via arterial line) and heart rate/ECG.
* **Perfusion:** Monitor peripheral pulses, skin color/temperature, and urine output.
* **Administration Site:** Frequent checks for extravasation at the IV site. Central venous access is preferred.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately and infiltrate the area with **phentolamine** (alpha-adrenergic antagonist) to prevent necrosis.
* **Concentration:** Ensure clear communication of concentration (always use mcg/kg/min or mcg/min, never ml/hr, to minimize dosing errors).
* **Site Preference:** Avoid peripheral infusion if possible; if necessary, use a large-bore proximal vein for the shortest duration possible.
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*Disclaimer: This information is for educational purposes only. Drug dosing, administration protocols, and safety guidelines can change based on institutional policy, regional standards, and evolving clinical data. Always verify specific dosing and compatibility information using current local protocols and professional references (e.g., UpToDate, Lexicomp, or hospital pharmacy) before prescribing.*
