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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 septic shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Adjunct treatment during cardiac arrest (rarely first-line).
## Adult Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous infusion.
* **Titration:** Titrate by 0.05 to 0.1 mcg/kg/min every 2–5 minutes to achieve target mean arterial pressure (MAP), typically ≥65 mmHg.
* **Maintenance:** 0.01 to 3 mcg/kg/min (highly variable; doses >1 mcg/kg/min suggest refractory shock).
* **Standard Concentration:** Often 4 mg/250 mL or 8 mg/250 mL D5W or NS.
## Pediatric Dosing
* **Initial:** 0.05 to 0.1 mcg/kg/min continuous infusion.
* **Titration:** Titrate to clinical effect; usual range 0.05 to 1 mcg/kg/min.
* *Note: Always verify concentration and infusion pump settings per institutional pediatric protocols.*
## Dose Adjustments
* **Renal/Hepatic:** No formal dose adjustments; monitor for systemic ischemia.
* **Geriatric:** Use the lowest effective dose; higher susceptibility to adverse cardiovascular effects.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites (in some formulations).
* Hypotension due to uncorrected blood volume deficit (hypovolemia must be repleted first).
## Adverse Effects
* **Common:** Hypertension, headache, anxiety.
* **Serious:** Tissue necrosis/gangrene upon extravasation (treat with phentolamine), arrhythmias (bradycardia or tachycardia), limb ischemia, mesenteric ischemia.
## Key Drug Interactions
* **MAO Inhibitors/TCAs:** May cause severe, prolonged hypertensive crisis.
* **Beta-blockers:** May result in unopposed alpha-adrenergic-mediated vasoconstriction (severe hypertension).
* **Cyclopropane/Halothane Anesthetics:** Increases risk of ventricular arrhythmias.
## Monitoring
* **Continuous:** Blood pressure (ideally via intra-arterial line), heart rate, ECG.
* **Perfusion:** MAP, urine output, skin temperature, capillary refill, and lactate levels.
* **Site:** Inspect IV site frequently for signs of extravasation.
## Clinical Pearls
* **Extravasation Management:** Stop infusion immediately. If available, infiltrate the area with phentolamine (5–10 mg in 10 mL saline) locally.
* **Administration:** It is preferred to administer via a central venous catheter to prevent necrosis, though large-bore peripheral access may be used briefly in emergency settings per specific hospital protocols.
* **Compatibility:** Administer only through dedicated lines; do not mix with sodium bicarbonate or alkaline solutions as they inactivate norepinephrine.
* **Weaning:** Wean gradually to prevent rebound hypotension.
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**Educational Disclaimer:** This information is for educational purposes only and does not supersede local institutional protocols. Verify all dosing, compatibility, and infusion guidelines with current drug references (e.g., Lexicomp, Micromedex) or your hospital pharmacy department before prescribing or administering.
