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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent that acts on alpha-1 adrenergic receptors causing vasoconstriction, and beta-1 adrenergic receptors increasing cardiac contractility and heart rate. It is primarily used to treat severe hypotension and shock.
## Primary Indications
* Severe hypotension requiring vasopressor support.
* Cardiogenic shock.
* Septic shock.
## Adult Dosing
* **Intravenous Infusion:** Typically initiated at 0.01 to 0.02 mcg/kg/min, titrated upwards to achieve the desired blood pressure.
* **Usual effective dose range:** 0.01 to 0.3 mcg/kg/min.
* **Maximum dose:** Doses higher than 0.3 mcg/kg/min are sometimes used but are associated with increased risk of adverse events. Specific maximums may vary by protocol.
## Pediatric Dosing
* **Intravenous Infusion:** Initial dose of 0.05 to 0.1 mcg/kg/min, titrated to effect.
* **Usual effective dose range:** 0.05 to 0.2 mcg/kg/min.
* **Maximum dose:** May be increased up to 1 mcg/kg/min in refractory hypotension, under close monitoring. Specific maximums may vary by protocol.
## Dose Adjustments
No specific dose adjustments are routinely recommended for hepatic or renal impairment. However, careful titration based on patient response is crucial in all populations.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotensive patients with mechanical obstruction to cardiac outflow (e.g., severe aortic stenosis).
* Use of cyclopropane or halogenated hydrocarbon anesthetics (risk of severe arrhythmias).
## Adverse Effects
* **Common:** Tachycardia, bradycardia (reflex), arrhythmias, hypertension, headache, anxiety, peripheral ischemia, extravasation leading to tissue necrosis.
* **Less Common:** Dizziness, shortness of breath, nausea, vomiting, decreased cardiac output.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) & Tricyclic Antidepressants (TCAs):** Potentiate the pressor response. Discontinue MAOIs at least 14 days prior to norepinephrine initiation.
* **Anesthetics (volatile):** Increased risk of arrhythmias.
* **Alpha and Beta Blockers:** Can antagonize or complicate the effects of norepinephrine.
* **Ergot Alkaloids:** Increased risk of severe peripheral vasoconstriction.
## Monitoring
* **Hemodynamics:** Blood pressure (continuous arterial monitoring preferred), heart rate, cardiac output if available.
* **Perfusion:** Urine output, mental status, capillary refill, lactate levels.
* **Infusion Site:** For signs of extravasation (use phentolamine for extravasation management).
* **ECG:** For arrhythmias.
## Clinical Pearls
* Norepinephrine is a potent vasoconstrictor; monitor closely for signs of peripheral ischemia.
* Always administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue infusion immediately, aspirate any residual drug, and infiltrate the area with phentolamine.
* The choice of vasopressor and specific dosing regimens for septic shock are often guided by institutional protocols and patient response.
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*Disclaimer: This information is intended for clinical use and does not replace the most current prescribing information. Always verify current prescribing information with the official product insert and institutional guidelines.*
