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# Norepinephrine
## Overview
Norepinephrine is a potent alpha-1 adrenergic agonist and a weaker beta-1 adrenergic agonist. It causes vasoconstriction, which increases systemic vascular resistance and blood pressure. It also has a mild positive inotropic and chronotropic effect on the heart.
## Primary Indications
* Severe hypotension and shock (e.g., septic shock, cardiogenic shock) refractory to initial fluid resuscitation.
## Adult Dosing
* **Intravenous infusion:** Typically initiated at **2 mcg/min to 10 mcg/min**. Doses can be titrated based on patient response (mean arterial pressure [MAP] goal, typically MAP ≥ 65 mmHg). Doses may range from **0.01 mcg/kg/min to 2 mcg/kg/min** or higher in some cases. The exact starting dose and titration range often depend on local protocols and patient hemodynamics.
## Pediatric Dosing
* **Intravenous infusion:** Typically initiated at **0.05 mcg/kg/min to 0.1 mcg/kg/min**. Doses can be titrated based on patient response, with usual maintenance doses ranging from **0.05 mcg/kg/min to 1 mcg/kg/min**. Higher doses may be required in some cases. The exact starting dose and titration range often depend on local protocols and patient hemodynamics.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, as it is primarily metabolized in the liver and tissues.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to absolute or relative hypovolemia unless used as a temporizing measure prior to volume resuscitation.
* During general anesthesia with cyclopropane or halothane.
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, tissue necrosis (extravasation), reduced cardiac output at higher doses.
* **Other:** Headache, anxiety, dizziness, dyspnea.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiated hypertensive crisis. Avoid concurrent use. If necessary, use extreme caution and reduced doses.
* **Tricyclic Antidepressants (TCAs):** Potentiated hypertensive crisis. Avoid concurrent use. If necessary, use extreme caution and reduced doses.
* **Ergot alkaloids, oxytocic drugs:** Prolonged, severe hypertension and potential gangrene.
* **Beta-blockers:** May blunt the pressor response to norepinephrine.
## Monitoring
* **Hemodynamics:** Continuous arterial blood pressure monitoring is essential. Monitor heart rate, cardiac rhythm, and central venous pressure if available.
* **Urine Output:** Assess renal perfusion.
* **Signs of peripheral ischemia:** Monitor extremities for color, temperature, and capillary refill.
* **Infusion site:** Monitor closely for signs of extravasation.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately and infiltrate the area with phentolamine.
* Norepinephrine is light-sensitive and should be protected from light during administration.
* Gradually titrate doses to achieve target MAP, and then taper slowly to avoid rebound hypotension.
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*This information is intended for clinical use and does not replace the need to consult the official prescribing information and institutional protocols. Always verify current drug information before use.*
