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# Norepinephrine
## Overview
Norepinephrine is a sympathomimetic amine that acts primarily as an alpha-adrenergic agonist, causing vasoconstriction and increasing peripheral vascular resistance. It also has some beta-1 adrenergic activity, which can increase myocardial contractility and heart rate.
## 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 2-4 mcg/minute via continuous intravenous infusion. Titrate to achieve target mean arterial pressure (MAP) of 65-70 mmHg or as per local protocol. Usual maintenance doses range from 0.1 to 2 mcg/kg/minute. Maximum dose is generally considered to be 1 mcg/kg/minute, but higher doses may be used in refractory shock under close supervision.
* **Cardiac Arrest:** 1 mg IV/IO every 3-5 minutes.
## Pediatric Dosing
* **Hypotension/Shock:** 0.05-0.1 mcg/kg/minute IV infusion, titrate upwards as needed to a maximum of 1-2 mcg/kg/minute. Dosing is highly individualized and dependent on clinical response.
* **Cardiac Arrest:** 0.01 mg/kg IV/IO (10 mcg/kg), maximum single dose 1 mg. Repeat every 3-5 minutes.
## Dose Adjustments
No specific dose adjustments are routinely recommended for hepatic or renal impairment, as norepinephrine is rapidly metabolized. However, close monitoring of hemodynamic response is crucial in patients with these conditions.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use during cyclopropane or halogenated hydrocarbon anesthesia (risk of severe hypertension and arrhythmias).
* Inadequate circulating blood volume prior to initiating therapy (correct volume deficit first).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, myocardial ischemia, peripheral ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness.
* **Respiratory:** Dyspnea.
* **Other:** Decreased urine output.
## Key Drug Interactions
* **MAO Inhibitors and Tricyclic Antidepressants:** Potentiate the pressor effects of norepinephrine; should be discontinued at least 10-14 days prior to initiating norepinephrine.
* **Anesthetics (e.g., Halothane, Cyclopropane):** Increased risk of arrhythmias.
* **Beta-blockers:** May unmask unopposed alpha-adrenergic stimulation leading to severe hypertension.
* **Alpha-blockers:** May reduce the pressor effect.
* **Oxytocics:** Can cause severe hypertension.
## Monitoring
* Continuous hemodynamic monitoring (blood pressure, heart rate).
* Urine output.
* Central venous pressure (if available).
* Signs of peripheral perfusion (e.g., skin color, temperature, capillary refill).
* Infusion site for signs of extravasation.
## Clinical Pearls
* Always correct hypovolemia before or concurrently with norepinephrine administration.
* Norepinephrine should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis. If only a peripheral line is available, ensure it is in a large vein and monitor the site closely.
* Phentolamine is the recommended antidote for extravasation.
* Titrate carefully to achieve the desired hemodynamic effect without causing excessive hypertension.
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*This information is intended for healthcare professionals and does not substitute for clinical judgment. Always consult the official prescribing information and relevant guidelines for complete and up-to-date information before making any treatment decisions.*
