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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine and vasopressor that acts primarily on alpha-1 adrenergic receptors, causing vasoconstriction and increasing peripheral vascular resistance. It also has some beta-1 adrenergic activity, which can increase heart rate and contractility, though this effect is less pronounced than its alpha-1 mediated effects.
## Primary Indications
* Treatment of hypotension and shock, particularly distributive shock (e.g., septic shock, neurogenic shock).
* Adjunct in cardiac arrest.
## Adult Dosing
* **Hypotension/Shock:** Typically initiated at 0.01 to 0.03 mcg/kg/min IV infusion. Doses can be titrated upwards based on response, with typical maintenance doses ranging from 0.01 to 0.3 mcg/kg/min. Maximum recommended doses vary by protocol but may range from 0.3 to 1 mcg/kg/min. Titration should be guided by hemodynamic parameters and clinical response.
* **Cardiac Arrest:** 1 mg IV/IO every 3-5 minutes.
## Pediatric Dosing
* **Hypotension/Shock:** 0.05 to 0.1 mcg/kg/min IV infusion. Doses can be titrated up to 0.2-2 mcg/kg/min based on clinical response.
* **Cardiac Arrest:** 0.01 mg/kg IV/IO (10 mcg/kg), maximum 1 mg. May repeat every 3-5 minutes.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential as clearance may be reduced.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to hypovolemia unless used as a temporizing measure until volume resuscitation is achieved.
* Use during cyclopropane or halogenated hydrocarbon anesthesia due to potential for severe hypertension and arrhythmias.
## Adverse Effects
* **Cardiovascular:** Arrhythmias (including ventricular arrhythmias), bradycardia (reflex), hypertension, peripheral ischemia, palpitations, tachycardia.
* **Local:** Extravasation can cause severe tissue necrosis; infiltration with phentolamine is recommended.
* **Other:** Headache, anxiety, confusion, dizziness, tremors, dyspnea, potential for increased blood glucose.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiates pressor response, leading to hypertensive crisis. Avoid concomitant use or use extreme caution with significantly reduced norepinephrine doses if unavoidable.
* **Tricyclic Antidepressants (TCAs):** May potentiate the pressor response.
* **Beta-blockers:** May cause unopposed alpha-stimulation, leading to severe hypertension.
* **General Anesthetics (e.g., Halogenated hydrocarbons):** Increased risk of arrhythmias.
* **Ergot Alkaloids, Oxytocin:** May cause severe hypertension.
* **Alpha-adrenergic Blockers:** May antagonize the pressor effect.
## Monitoring
* **Hemodynamics:** Blood pressure, heart rate, cardiac output (if available).
* **Perfusion:** Urine output, peripheral pulses, skin color and temperature, capillary refill.
* **Electrolytes:** Especially potassium.
* **Blood Glucose:** Monitor for hyperglycemia.
* **Infusion Site:** For signs of extravasation.
## Clinical Pearls
* Norepinephrine is a potent vasoconstrictor and should be infused via a central venous catheter whenever possible to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue the infusion immediately and infiltrate the affected area with phentolamine.
* Titrate infusion rates based on the patient's response, aiming for adequate tissue perfusion and blood pressure, rather than a specific target number.
* Norepinephrine is light-sensitive; protect solutions from light during infusion.
* Ensure adequate fluid resuscitation before or concurrently with norepinephrine administration in cases of hypovolemia.
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*Disclaimer: This information is intended for clinical pharmacy use and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols for definitive guidance. Drug information is constantly evolving.*
