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# Norepinephrine (Levarterenol)
## Overview
Norepinephrine is a potent catecholamine acting primarily as an alpha-1 adrenergic agonist with moderate beta-1 agonist activity. It causes intense peripheral vasoconstriction and increased myocardial contractility. It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Cardiac arrest (less common, usually via advanced life support algorithms).
## Adult Dosing
* **Initial:** 0.01 to 0.05 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate to achieve target mean arterial pressure (MAP), typically >65 mmHg. Usual maintenance range is 0.05 to 0.5 mcg/kg/min.
* **Maximum:** Doses exceeding 3 mcg/kg/min are occasionally used in refractory shock but carry significant risk of severe peripheral ischemia.
* *Note: Dosing is highly dependent on institutional protocols and clinical hemodynamic goals.*
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.05 to 0.1 mcg/kg/min every 5–15 minutes based on blood pressure response.
* **Usual Max:** Often capped at 1–2 mcg/kg/min, though higher doses are used in specialized intensive care settings.
## Dose Adjustments
* **Renal/Hepatic:** No specific dosage adjustments provided in manufacturers' labeling; however, clinical response should guide titration.
* **Discontinuation:** Must be tapered slowly to avoid precipitous drop in blood pressure.
## Contraindications
* Hypersensitivity to norepinephrine or sulfite-containing products.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary/cerebral perfusion while fluid resuscitation is initiated).
* Mesenteric or peripheral vascular thrombosis (due to risk of increasing ischemia).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (bradycardia or tachycardia), exacerbation of ischemia.
* **Local:** Extravasation necrosis (use a central line whenever possible).
* **Systemic:** Limb ischemia, anxiety, headache, respiratory distress.
## Key Drug Interactions
* **MAO Inhibitors/TCAs:** May cause severe, prolonged hypertension.
* **Beta-blockers:** May result in unopposed alpha-adrenergic stimulation, leading to extreme hypertension and reflex bradycardia.
* **Cyclopropane/Halogenated Hydrocarbon Anesthetics:** Increased risk of ventricular arrhythmias.
## Monitoring
* **Clinical:** Continuous blood pressure monitoring (preferably via arterial line).
* **Vascular:** Frequent assessment of IV site for extravasation; monitor peripheral perfusion (capillary refill, extremity warmth/color).
* **Laboratory:** Serum lactate, heart rate/rhythm via ECG, and urine output (as a surrogate for end-organ perfusion).
## Clinical Pearls
* **Extravasation:** If infiltration occurs, stop infusion immediately. Consider local infiltration of phentolamine (5–10 mg in 10 mL saline) to minimize necrosis.
* **Administration:** Must be administered via a central venous line whenever possible to prevent tissue necrosis; avoid small peripheral veins for long-term use.
* **Compatibility:** Highly concentrated norepinephrine should be diluted in D5W or D5NS; pH sensitivity makes it unstable in alkaline solutions.
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*Disclaimer: This information is for educational purposes only. Clinical practice varies by institution; always consult local pharmacy protocols and the official, most current manufacturer prescribing information before administration.*
