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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with alpha-1 agonist activity (vasoconstriction) and moderate beta-1 agonist activity (inotropy). It is the first-line vasopressor for most forms of shock.
## Primary Indications
* Acute hypotensive states (e.g., septic shock, cardiogenic shock).
* Adjunct treatment during cardiac arrest.
## Adult Dosing
* **Initial:** 0.01–0.05 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate by 0.01–0.05 mcg/kg/min every 3–5 minutes until target mean arterial pressure (MAP) is achieved (typically 65 mmHg).
* **Maintenance:** Usual range 0.05–0.5 mcg/kg/min.
* **Max:** No absolute clinical maximum; doses >1 mcg/kg/min are considered high-dose and carry significantly increased risks of refractory shock and organ ischemia.
## Pediatric Dosing
* **Initial:** 0.05–0.1 mcg/kg/min continuous IV infusion.
* **Titration:** Titrate in increments of 0.05 mcg/kg/min as needed.
* **Max:** Typically 1–2 mcg/kg/min. *Always verify against local weight-based institutional protocols.*
## Dose Adjustments
* **Hepatic/Renal:** No specific dosing adjustments provided; however, careful monitoring is required as these patients may have altered hemodynamics.
* **Discontinuation:** Always taper gradually to avoid rebound hypotension.
## Contraindications
* Hypersensitivity to norepinephrine or bisulfites.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary/cerebral perfusion until fluid resuscitation is completed).
## Adverse Effects
* **Cardiovascular:** Hypertension, arrhythmias (bradycardia or tachycardia), limb ischemia.
* **Local:** Extravasation necrosis (use a central line whenever possible).
* **Metabolic:** Hyperglycemia, lactic acidosis (at high doses).
## Key Drug Interactions
* **MAO Inhibitors/Antidepressants:** May cause severe, prolonged hypertensive crisis.
* **Beta-blockers:** May result in excessive alpha-mediated vasoconstriction and reflex bradycardia.
* **General Anesthetics (e.g., Halothane/Cyclopropane):** Increased risk of ventricular arrhythmias.
## Monitoring
* **Continuous arterial pressure monitoring** preferred.
* **Heart rate and ECG** for arrhythmias.
* **Perfusion markers:** Urine output, capillary refill, capillary lactate levels, and neuro-status.
* **Extravasation:** Frequent assessment of IV site. If extravasation occurs, administer phentolamine locally.
## Clinical Pearls
* **Central access:** Always prefer central venous access. If administered peripherally, use a large vein (antecubital fossa), limit duration, and use low concentrations.
* **Compatibility:** Administer only via central line when managing septic shock to avoid skin sloughing.
* **Dosing protocol:** Always follow site-specific titration guidelines; many hospitals have predefined "norepinephrine drip" concentrations (e.g., 4mg/250mL or 8mg/250mL) to prevent calculation errors.
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**Disclaimer:** This information is for educational purposes only. Always consult your institution’s clinical guidelines, the current Package Insert, or a pharmacist before prescribing or administering medication. Dosing and clinical status should be evaluated on an individual, patient-specific basis.
