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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 on beta-1 adrenergic receptors, increasing heart rate and contractility. It is used to treat severe hypotension and shock.
## Primary Indications
* Treatment of septic shock.
* Treatment of neurogenic shock.
* Treatment of other distributive shock states.
* Management of severe hypotension unresponsive to fluid resuscitation.
## Adult Dosing
* **Initial Dose:** 2 to 10 mcg/minute via continuous IV infusion.
* **Titration:** Titrate infusion rate to achieve and maintain a target mean arterial pressure (MAP) of 65 mmHg or higher. Doses may be increased up to 30 mcg/minute or higher in refractory cases, guided by patient response and institutional protocols.
* **Administration:** Always administered via a central venous catheter to reduce the risk of extravasation and tissue necrosis. Peripheral administration is generally not recommended due to risk of severe vasoconstriction and tissue ischemia, but may be considered in dire emergencies for short durations while a central line is being placed, with close monitoring.
## Pediatric Dosing
* **Initial Dose:** 0.05 to 0.1 mcg/kg/minute via continuous IV infusion.
* **Titration:** Titrate infusion rate to achieve and maintain a target MAP greater than or equal to the patient's gestational age plus 2 mmHg (for neonates) or a target SBP of 70 mmHg plus 2 times the patient's age in years (for children up to 10 years), or 90 mmHg for children older than 10 years. Doses may be increased up to 1 mcg/kg/minute or higher based on institutional guidelines and patient response.
* **Administration:** Central venous access is preferred.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically required, but patients may be more sensitive to vasopressor effects.
* **Hepatic Impairment:** No specific dose adjustment is typically required, but patients may be more sensitive to vasopressor effects.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension secondary to hypovolemia unless used as a temporizing measure to maintain coronary and cerebral perfusion until adequate volume replacement is achieved.
* In general, concurrent use with certain anesthetic agents (e.g., cyclopropane, halothane) that sensitize the heart to catecholamines should be avoided due to risk of arrhythmias.
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, angina, decreased cardiac output at higher doses, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Metabolic:** Hyperglycemia.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiates the pressor response; avoid concurrent use. If unavoidable, administer with extreme caution and reduced doses.
* **Tricyclic Antidepressants (TCAs):** May potentiate the pressor response.
* **Beta-Blockers:** May blunt the beta-1 (inotropic) effects of norepinephrine while unopposed alpha-1 effects could lead to severe peripheral vasoconstriction.
* **Alpha-Blockers:** May reduce the pressor effects.
* **Ergot Alkaloids:** May potentiate the vasoconstrictive effects.
* **Oxytocin:** May potentiate the pressor effects.
## Monitoring
* **Hemodynamics:** Continuous ECG, invasive arterial blood pressure monitoring (MAP), central venous pressure.
* **Perfusion:** Urine output, capillary refill, skin temperature and color.
* **Metabolic:** Blood glucose.
* **Infusion Site:** Assess for signs of extravasation.
## Clinical Pearls
* Norepinephrine is a first-line agent for septic shock.
* It has a relatively short half-life, so continuous infusion and careful titration are essential.
* Prompt recognition and management of extravasation are critical to prevent tissue necrosis. If extravasation occurs, discontinue the infusion and initiate local treatment, often with phentolamine.
* The goal of therapy is to restore adequate tissue perfusion, not necessarily a specific MAP target in all patients. Individualize targets based on patient condition.
* Concurrent use with phenylephrine may be considered for refractory hypotension, but increases the risk of excessive alpha-adrenergic stimulation.
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**Disclaimer:** This information is intended for clinical professionals and does not replace comprehensive drug compendia or institutional protocols. Always consult current prescribing information and local guidelines before administering medications.
