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# Norepinephrine
## Overview
Norepinephrine is a vasopressor agent that stimulates alpha-adrenergic receptors, causing vasoconstriction and increasing peripheral vascular resistance and blood pressure. It also has some beta-1 adrenergic receptor activity, increasing heart rate and contractility.
## Primary Indications
* Treatment of hypotension (low blood pressure) unresponsive to adequate fluid resuscitation.
* Often used in shock states such as septic shock, cardiogenic shock, and anaphylactic shock.
## Adult Dosing
* **Intravenous infusion:** Typically initiated at 0.01 to 0.02 mcg/kg/min.
* **Titration:** Dose is adjusted based on patient response (e.g., mean arterial pressure, heart rate) and may be increased up to 0.1 mcg/kg/min. Higher doses (up to 0.2 mcg/kg/min or more) may be used in refractory cases, but this depends heavily on institutional protocol and patient-specific monitoring.
* **Maximum dose:** No strict maximum is defined, as titration is guided by clinical response and potential adverse effects.
## Pediatric Dosing
* **Intravenous infusion:** Typically initiated at 0.05 to 0.1 mcg/kg/min.
* **Titration:** Dose is adjusted based on patient response and may be increased up to 1 mcg/kg/min. Some protocols may recommend higher doses in refractory shock. Exact dosing and titration parameters are highly dependent on institutional protocols and patient condition.
## Dose Adjustments
Dose adjustments are primarily based on achieving target blood pressure and clinical response. No specific dose adjustments are typically required for hepatic or renal impairment, but patients with these conditions may be more susceptible to adverse effects.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use with extreme caution in patients with sulfite sensitivity.
* Generally not recommended in patients with mesenteric or peripheral vascular thrombosis due to risk of increasing ischemia.
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, tachycardia, chest pain, peripheral ischemia, digital ischemia, extravasation leading to tissue necrosis.
* **Other:** Headache, anxiety, tremor, dizziness, shortness of breath, nausea, vomiting.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Potentiate the pressor response; avoid concurrent use or use with extreme caution and significantly reduced doses.
* **Anesthetic agents (e.g., cyclopropane, halothane):** May increase myocardial irritability and risk of arrhythmias.
* **Beta-blockers:** May unmask unopposed alpha-stimulation, leading to severe hypertension.
* **Alpha-blockers:** May decrease the pressor effect.
## Monitoring
* **Hemodynamic parameters:** Continuous blood pressure monitoring (arterial line preferred for titration), heart rate, central venous pressure (if available).
* **Perfusion:** Assess peripheral circulation, urine output, mental status, and lactate levels.
* **Infusion site:** Closely monitor for signs of extravasation.
* **Cardiac rhythm:** Continuous ECG monitoring.
## Clinical Pearls
* Always administer via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, discontinue infusion immediately and administer phentolamine locally to the affected area.
* Norepinephrine is light-sensitive; protect infusions from light.
* Titrate to the lowest effective dose that achieves target mean arterial pressure (MAP), often 65 mmHg in sepsis, but this may vary by protocol.
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*Disclaimer: This information is intended for clinical pharmacy professionals and is not a substitute for comprehensive drug information resources or professional judgment. Always consult the most current prescribing information and institutional protocols before administering any medication.*
