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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 cardiac output.
## Primary Indications
* Management of severe hypotension and shock, particularly in septic shock and distributive shock.
## Adult Dosing
* **Intravenous infusion:** Typically initiated at 0.01 to 0.02 mcg/kg/min.
* **Titration:** Titrate to achieve and maintain a target mean arterial pressure (MAP) of 65 mmHg or higher. Doses may range from 0.01 to 3 mcg/kg/min.
* **Maximum dose:** Higher doses (e.g., > 1 mcg/kg/min) are sometimes used in severe shock but are associated with increased risk. Specific maximums are often determined by clinical response and local protocol.
## Pediatric Dosing
* **Intravenous infusion:** Typically initiated at 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate to achieve and maintain adequate blood pressure and perfusion. Doses may range from 0.05 to 2 mcg/kg/min. Specific target blood pressure may vary by age and clinical condition.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential as efficacy and toxicity may be altered.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but careful monitoring is essential as efficacy and toxicity may be altered.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe hypotension with distributive shock unresponsive to fluid resuscitation.
* Use of cyclopropane or halogenated hydrocarbon anesthetics, which may sensitize the myocardium to the arrhythmogenic effects of catecholamines.
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, chest pain, peripheral ischemia, digital ischemia, myocardial infarction, decreased blood flow to vital organs.
* **Other:** Anxiety, headache, dizziness, tremor, dyspnea, nausea, vomiting.
* **Extravasation:** Can cause severe tissue necrosis and sloughing.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** May potentiate the pressor response; concurrent use should be avoided or used with extreme caution and lower initial doses.
* **Alpha and Beta Blockers:** May antagonize the effects of norepinephrine.
* **Anesthetics (especially halogenated):** Increased risk of arrhythmias.
## Monitoring
* Continuous blood pressure monitoring is essential.
* Heart rate and rhythm.
* Central venous pressure or pulmonary artery catheterization if available.
* Urine output.
* Peripheral perfusion and signs of ischemia.
* Infusion site 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, discontinue the infusion immediately and administer phentolamine as a local subcutaneous injection to the affected area.
* Adequate fluid resuscitation should be initiated and optimized before or concurrently with norepinephrine administration in cases of shock.
* The choice of vasopressor and specific dosing targets in shock are often guided by institutional protocols and clinical guidelines.
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**Disclaimer:** This information is intended for clinical professionals. Always verify current prescribing information and consult with a pharmacist or physician for specific patient care decisions. Dosing recommendations may vary based on patient-specific factors and local protocols.
