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# Norepinephrine
## Overview
A potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 adrenergic receptors (inotropy). It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states.
* First-line agent in septic shock.
* Cardiac arrest (as an alternative to epinephrine in specific protocols).
## Adult Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min via continuous IV infusion.
* **Titration:** Titrate to goal Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Common Range:** 0.01 to 3 mcg/kg/min.
* **Max:** No absolute maximum; doses >1–2 mcg/kg/min are associated with significant risk of refractory shock and organ ischemia.
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate to effect (usually MAP/SBP goals based on age-specific norms).
* **Max:** Generally up to 1–2 mcg/kg/min.
* *Note: Dosing is highly dependent on institutional pediatric critical care protocols.*
## Dose Adjustments
* **Renal/Hepatic:** No specific dose adjustments provided; use caution, as patients with organ failure may have altered perfusion and increased sensitivity.
* **Hypovolemia:** Correct intravascular volume depletion prior to or concurrent with initiation.
## Contraindications
* Hypersensitivity to norepinephrine or any component.
* Mesenteric or peripheral vascular thrombosis (relative contraindication due to risk of ischemia).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (tachycardia or bradycardia), myocardial ischemia.
* **Local:** Extravasation can cause severe tissue necrosis and sloughing.
* **Metabolic:** Metabolic acidosis, hyperglycemia.
* **Other:** Reduced peripheral perfusion (digits, viscera, kidneys).
## Key Drug Interactions
* **MAO Inhibitors/Tricyclic Antidepressants:** May cause severe, prolonged hypertension; dose reduction of norepinephrine is required.
* **Beta-blockers:** May cause excessive alpha-adrenergic stimulation leading to extreme hypertension and reflex bradycardia.
* **Anesthetics (Halogenated hydrocarbons):** Increased propensity for cardiac arrhythmias.
## Monitoring
* **Continuous:** ECG, blood pressure (preferably via arterial line), and heart rate.
* **Clinical:** Urine output, extremity perfusion, mental status, and lactate levels (as a marker of tissue perfusion).
* **Site:** Strict monitoring of IV site for signs of extravasation.
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, discontinue infusion and infiltrate the area with phentolamine (alpha-adrenergic antagonist) to minimize tissue necrosis.
* **Administration:** Must be administered via a large peripheral vein (short-term only, if absolutely necessary) or a central venous catheter.
* **Dosing Calculation:** Always confirm concentration (typically 4 mg/250 mL or 8 mg/250 mL) and titrate based on the infusion pump settings per protocol.
* **Weaning:** Wean slowly to avoid rebound hypotension once the underlying cause of shock begins to resolve.
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**Disclaimer:** This information is for educational purposes only. Always verify doses, contraindications, and local institutional protocols with current prescribing information (e.g., Lexicomp, Micromedex) and your clinical pharmacist before administration.
