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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and moderate beta-1 adrenergic agonist activity (inotropic effect). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Adjunct during cardiac arrest.
## Adult Dosing
* **Initial:** 0.01 mcg/kg/min to 0.05 mcg/kg/min via continuous IV infusion.
* **Titration:** Titrate by 0.01 to 0.05 mcg/kg/min every 2–5 minutes to achieve target mean arterial pressure (MAP, typically ≥65 mmHg).
* **Typical Maintenance Range:** 0.05 mcg/kg/min to 0.5 mcg/kg/min.
* **Maximum:** No fixed pharmacological maximum; doses exceeding 1–2 mcg/kg/min are associated with severe peripheral ischemia and refractory shock. Local institutional protocols must be followed for escalation limits.
## Pediatric Dosing
* **Initial:** 0.05 mcg/kg/min to 0.1 mcg/kg/min by continuous IV infusion.
* **Titration:** Titrate to clinical effect.
* **Range:** 0.05 mcg/kg/min to 2 mcg/kg/min.
* **Note:** Always verify weight-based dosing per institutional hemodynamic support protocols.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No standard dosage adjustment required, but patients may have altered sensitivity to catecholamines.
* **Severe Peripheral Ischemia:** Reduce dose or discontinue if signs of end-organ hypoperfusion (mottling, cold extremities) occur.
## Contraindications
* Hypersensitivity to norepinephrine or sulfite-containing products.
* Mesenteric or peripheral vascular thrombosis (relative contraindication due to risk of increasing ischemia).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, myocardial ischemia.
* **Local:** Extravasation can lead to tissue necrosis and gangrene.
* **Metabolic:** Elevated lactic acid (due to peripheral hypoperfusion/beta-adrenergic stimulation).
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May result in severe, prolonged hypertension.
* **Beta-Blockers:** May cause unopposed alpha-adrenergic stimulation, leading to excessive vasoconstriction and hypertension.
* **Halogenated Hydrocarbons (e.g., Cyclopropane, Halothane):** Increase myocardial irritability and risk of arrhythmias.
## Monitoring
* **Continuous ECG:** Monitor for tachycardia/arrhythmias.
* **Arterial Line:** Recommended for frequent blood pressure monitoring and titration.
* **Site Check:** Monitor IV site continuously for signs of extravasation. If extravasation occurs, administer phentolamine locally.
* **Perfusion:** Monitor urine output, peripheral perfusion, and serum lactate.
## Clinical Pearls
* **Administration:** Must be administered via a large central vein whenever possible to minimize risk of extravasation.
* **Compatibility:** Highly acidic; check compatibility with other concurrent medications in the same line.
* **Tapering:** Avoid abrupt discontinuation to prevent rebound hypotension; wean as the patient’s underlying condition stabilizes.
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*Disclaimer: This information is for educational purposes only. Dosing and clinical protocols vary by institution. Always verify specific dosing, safety, and compatibility information against the most recent manufacturer prescribing information and local hospital policy before administration.*
