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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine that acts primarily as an alpha-adrenergic agonist, causing vasoconstriction, and also as a beta-1 adrenergic agonist, increasing heart rate and contractility. It is a vasopressor used to treat hypotension.
## Primary Indications
* Severe hypotension (e.g., shock, sepsis) refractory to adequate fluid resuscitation.
## Adult Dosing
* **Administration:** Intravenous infusion.
* **Starting Dose:** Typically 0.01 to 0.05 mcg/kg/minute.
* **Titration:** Gradually increase dose every 5-10 minutes to achieve target mean arterial pressure (MAP) of 65 mmHg or higher, or based on institutional protocol.
* **Maintenance Dose:** Doses can range from 0.01 to 3 mcg/kg/minute. Higher doses may be required in some patients.
* **Maximum Dose:** Doses up to 3 mcg/kg/minute are generally considered acceptable; higher doses are used with extreme caution and close monitoring.
## Pediatric Dosing
* **Administration:** Intravenous infusion.
* **Starting Dose:** Typically 0.05 to 0.1 mcg/kg/minute.
* **Titration:** Titrate to achieve target MAP of greater than or equal to the patient's age in years plus 2 mmHg, or based on institutional protocol.
* **Maintenance Dose:** Doses can range from 0.05 to 2 mcg/kg/minute.
* **Maximum Dose:** Doses up to 2 mcg/kg/minute are generally considered acceptable; higher doses are used with extreme caution.
## Dose Adjustments
* No dose adjustments are typically required for hepatic or renal impairment, as norepinephrine is metabolized in the liver and excreted by the kidneys, but its effects are primarily receptor-mediated. However, prolonged infusions may require careful monitoring in these populations.
## Contraindications
* Hypersensitivity to norepinephrine.
* Concurrent use with cyclopropane or halogenated hydrocarbon anesthetics due to increased risk of severe arrhythmias.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, peripheral ischemia, extravasation (leading to tissue necrosis).
* **Central Nervous System:** Headache, anxiety, tremor, dizziness.
* **Metabolic:** Hyperglycemia.
* **Other:** Cold extremities.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) & Tricyclic Antidepressants (TCAs):** Potentiate hypertensive effects; avoid concurrent use or use with extreme caution and reduced doses.
* **Anesthetics (e.g., Halogenated hydrocarbons):** Increased risk of arrhythmias.
* **Beta-blockers:** May reduce the beta-1 effects of norepinephrine, potentially leading to unopposed alpha-receptor stimulation and severe hypertension.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (arterial line preferred), heart rate, cardiac rhythm.
* **Perfusion:** Skin color and temperature, urine output, mental status.
* **Infusion Site:** For signs of extravasation.
* **Electrolytes and Glucose:** Especially with prolonged use.
## Clinical Pearls
* Administer via a central venous catheter to minimize risk of extravasation and tissue damage. If peripheral infusion is necessary, use a large vein and monitor the site very closely.
* Have phentolamine readily available for management of extravasation.
* Norepinephrine should be diluted in a compatible IV solution (e.g., D5W, NS) prior to infusion.
* Titrate infusion rate based on desired hemodynamic response, not solely on calculated dose per minute.
* Abrupt discontinuation can lead to precipitous drop in blood pressure; taper gradually if possible.
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**Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols for definitive guidance.
