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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and moderate beta-1 adrenergic activity (inotropy). It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotensive states (e.g., septic, cardiogenic, or distributive shock).
* Adjunct treatment during cardiac arrest (though epinephrine remains the primary agent).
## Adult Dosing
* **Initial:** 0.01–0.05 mcg/kg/min or 2–5 mcg/min continuous IV infusion.
* **Titration:** Titrate every 3–5 minutes by 0.05–0.1 mcg/kg/min or 2–5 mcg/min to maintain goal Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Maintenance:** Generally 0.01–3 mcg/kg/min.
* **Maximum:** No formal strict maximum; highly dependent on clinical context and refractory nature of shock. Refer to institutional protocol.
## Pediatric Dosing
* **Initial:** 0.05–0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min to achieve hemodynamic targets.
* **Maximum:** Typically 1–2 mcg/kg/min; higher doses may be required in specialized pediatric intensive care settings.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No specific adjustments provided by manufacturer. Monitor closely as hemodynamic response may be altered in organ failure.
* **Weaning:** Titrate down slowly based on clinical stability to avoid rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected blood volume deficit (except as emergency measure to maintain coronary/cerebral perfusion).
* Mesenteric or peripheral vascular thrombosis (due to risk of increasing ischemia).
## Adverse Effects
* **Common:** Hypertension, arrhythmias (tachycardia/bradycardia), headache, anxiety.
* **Severe:** Tissue necrosis and gangrene upon extravasation, limb ischemia, mesenteric ischemia.
## Key Drug Interactions
* **MAOIs/Tricyclic Antidepressants:** May cause severe, prolonged hypertension.
* **Beta-blockers:** May result in unopposed alpha-adrenergic stimulation, leading to excessive peripheral vasoconstriction and reflex bradycardia.
* **General Anesthetics (e.g., Cyclopropane/Halothane):** Increase cardiac sensitivity to catecholamines, raising arrhythmia risk.
## Monitoring
* **Hemodynamics:** Continuous MAP, heart rate, and rhythm (ECG).
* **Vascular Access:** **Must be administered via a central line** if possible. If peripheral line must be used, ensure large vein and monitor site continuously.
* **Perfusion:** Monitor extremity color/temperature, urine output (renal perfusion), and lactate levels (tissue perfusion).
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop the infusion immediately and administer phentolamine (5–10 mg in 10 mL saline, infiltrated into the area) to reverse vasoconstriction.
* **Compatibility:** Administer through a dedicated line to avoid drug-drug interactions. Norepinephrine is sensitive to light; avoid prolonged direct exposure.
* **Volume Status:** Norepinephrine should not be used as a substitute for adequate fluid resuscitation. Ensure optimal intravascular volume.
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**Educational Disclaimer:** This information is for educational purposes and reflects common clinical practice. Prescribing guidelines vary by hospital protocol and patient-specific factors. Always verify dosages, contraindications, and compatibility via the most current institutional formulary or official prescribing information (e.g., Package Insert/Lexicomp/Micromedex) before administration.
