Please check your internet connection and try again.
# Norepinephrine
## Overview
Norepinephrine (Levophed) is a potent alpha-1 adrenergic receptor agonist and a weaker beta-1 adrenergic receptor agonist. It causes vasoconstriction, leading to increased systemic vascular resistance and blood pressure.
## Primary Indications
* Severe hypotension and shock (e.g., septic shock, cardiogenic shock) refractory to adequate fluid resuscitation.
* Cardiogenic shock to increase blood pressure.
## Adult Dosing
* **Initial Infusion:** 0.01 to 0.02 mcg/kg/min.
* **Maintenance Infusion:** Titrate to achieve target mean arterial pressure (MAP), typically $\geq 65$ mmHg. Doses commonly range from 0.01 to 0.3 mcg/kg/min.
* **Maximum Dose:** Doses up to 1-2 mcg/kg/min have been used in refractory shock, but higher doses are associated with increased risk of adverse effects.
## Pediatric Dosing
* **Initial Infusion:** 0.05 to 0.1 mcg/kg/min.
* **Maintenance Infusion:** Titrate to achieve target MAP (e.g., $\geq$ 2 years old: MAP $>$ gestational age + 2 years mmHg; < 2 years old: MAP $>$ 50 mmHg). Doses commonly range from 0.1 to 1 mcg/kg/min.
* **Maximum Dose:** Doses up to 2 mcg/kg/min may be necessary.
*Note: Specific pediatric dosing can vary significantly based on patient condition and local protocols.*
## Dose Adjustments
* No dose adjustments are typically required for hepatic or renal impairment, as the drug is primarily metabolized by COMT and MAO in the liver and is largely cleared by the kidneys.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe hypotension due to relative hypovolemia unless used as a temporizing measure prior to or during volume resuscitation.
* Use of cyclopropane or halogenated hydrocarbon anesthetics (risk of severe arrhythmias).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), tachycardia, arrhythmias, peripheral ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Metabolic:** Hyperglycemia.
* **Other:** Dyspnea, pale skin.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiate the pressor effect of norepinephrine; concurrent use is contraindicated. If concurrent use is necessary, administer significantly reduced doses.
* **Tricyclic Antidepressants (TCAs) & Guanadrel/Guanethidine:** May potentiate the pressor response.
* **Alpha-adrenergic Blockers:** May reduce the pressor effect.
* **Beta-adrenergic Blockers:** May reduce the beta-mediated effects of norepinephrine.
* **Ergot Alkaloids and Oxytocics:** May cause severe hypertension.
* **Anesthetics (e.g., Cyclopropane, Halothane):** Increased risk of arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous monitoring of blood pressure (arterial line preferred), heart rate, and cardiac rhythm.
* **Infusion Site:** Assess for signs of extravasation.
* **Urine Output:** Monitor for adequate renal perfusion.
* **Laboratory:** Blood glucose, electrolytes.
## Clinical Pearls
* Administer via a central venous catheter to minimize risk of peripheral vasoconstriction and extravasation.
* If extravasation occurs, stop the infusion immediately and administer phentolamine locally to the affected area.
* Always ensure adequate intravascular volume before or concurrently with norepinephrine administration.
* Norepinephrine is a potent vasoconstrictor; titrate slowly to achieve desired hemodynamic goals.
* The effects of norepinephrine are generally short-lived upon discontinuation, but vigilance for changes is crucial.
***
*This information is intended for healthcare professionals. Please consult the most current prescribing information and relevant clinical guidelines for complete details before initiating therapy.*
