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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent that acts primarily on alpha-1 adrenergic receptors, causing vasoconstriction and increasing peripheral vascular resistance. It also has some beta-1 adrenergic activity, leading to increased heart rate and contractility.
## Primary Indications
* Treatment of hypotension, particularly in the setting of shock (e.g., septic shock, cardiogenic shock).
* Restoration and maintenance of blood pressure.
## Adult Dosing
* **Usual Starting Dose:** 0.01 to 0.02 mcg/kg/min intravenously.
* **Titration:** Increase dose in increments of 0.01 to 0.02 mcg/kg/min every 5-15 minutes as needed to achieve target blood pressure.
* **Usual Effective Range:** 0.01 to 0.3 mcg/kg/min.
* **Maximum Dose:** Doses up to 1 mcg/kg/min may be required in severe cases, but higher doses are associated with increased risk of adverse effects. Specific maximum doses may vary by institution and patient context.
## Pediatric Dosing
* **Usual Starting Dose:** 0.05 mcg/kg/min intravenously.
* **Titration:** Increase dose in increments of 0.05 to 0.2 mcg/kg/min every 5-15 minutes.
* **Usual Effective Range:** 0.05 to 1 mcg/kg/min.
* **Maximum Dose:** Doses up to 2 mcg/kg/min have been used in pediatric patients. Dosing is highly individualized and guided by institutional protocols and patient response.
## Dose Adjustments
* No specific dose adjustments are generally required for hepatic or renal impairment, as norepinephrine is rapidly metabolized. However, close monitoring of hemodynamic parameters is essential in all patients.
## Contraindications
* Hypersensitivity to norepinephrine.
* Concurrent use with cyclopropane or halogenated hydrocarbon anesthetics (risk of severe hypertension and arrhythmias).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), tachycardia, arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Other:** Dyspnea, decreased cardiac output with high doses.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** May potentiate the pressor effects of norepinephrine, leading to severe hypertension. Discontinue MAOIs at least 14 days prior to norepinephrine initiation.
* **Adrenergic Blockers (e.g., alpha-blockers, beta-blockers):** May alter the pressor and cardiac effects.
* **Oxytocics:** May cause severe hypertension.
* **Anesthetics (e.g., cyclopropane, halothane):** Increased risk of arrhythmias.
## Monitoring
* Continuous electrocardiogram (ECG) for arrhythmias.
* Continuous blood pressure monitoring (intra-arterial preferred for precise titration).
* Central venous pressure.
* Urine output.
* Peripheral perfusion (e.g., skin temperature, color, capillary refill).
* Assess 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, stop the infusion immediately and administer an alpha-adrenergic blocking agent, such as phentolamine, infiltrated into the affected area.
* Norepinephrine is light-sensitive and should be protected from light during infusion.
* The choice of vasopressor and its target blood pressure should be guided by the underlying cause of shock and institutional protocols.
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*Disclaimer: This information is intended for clinical professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional guidelines before making any treatment decisions.*
