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# Norepinephrine
## Overview
Norepinephrine is a potent sympathomimetic amine that acts as a vasopressor, primarily by stimulating alpha-adrenergic receptors, leading to peripheral vasoconstriction. It also has some beta-1 adrenergic receptor activity, increasing cardiac contractility and heart rate.
## Primary Indications
* Severe hypotension or shock unresponsive to adequate fluid resuscitation.
## Adult Dosing
* **Administration:** Continuous intravenous (IV) infusion.
* **Starting Dose:** Typically 0.01 to 0.05 mcg/kg/min.
* **Titration:** Titrate infusion rate to achieve target mean arterial pressure (MAP) or blood pressure. Common targets include MAP $\ge$ 65 mmHg or systolic blood pressure $\ge$ 90 mmHg.
* **Maximum Dose:** Generally, no strict maximum dose is established; titrate to effect. Doses up to 1 mcg/kg/min or higher may be required in severe shock.
## Pediatric Dosing
* **Administration:** Continuous IV infusion.
* **Starting Dose:** Typically 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate to achieve target blood pressure.
* **Maximum Dose:** Doses up to 1 mcg/kg/min or higher may be required. Dosing often guided by local protocol.
## Dose Adjustments
* No specific dose adjustments for renal or hepatic impairment. Dosing is primarily based on patient response and hemodynamic targets.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe hypotension with metabolic acidosis and hypoxemia (may worsen tissue perfusion).
## Adverse Effects
* **Cardiovascular:** Arrhythmias, hypertension, reflex bradycardia, peripheral ischemia, digital ischemia, chest pain, decreased cardiac output (at high doses).
* **Central Nervous System:** Headache, anxiety, tremor, dizziness.
* **Other:** Extravasation can cause severe tissue necrosis; monitor IV site closely.
## Key Drug Interactions
* **General Anesthetics:** May potentiate arrhythmias and hypertension.
* **MAO Inhibitors (MAOIs) and Tricyclic Antidepressants (TCAs):** Can potentiate the pressor effects of norepinephrine. Concomitant use is generally contraindicated or requires extreme caution and dose reduction.
* **Beta-Adrenergic Blockers:** May cause unopposed alpha-adrenergic stimulation, leading to severe hypertension.
* **Alpha-Adrenergic Blockers:** May attenuate the pressor effects.
* **Oxytocic Agents:** May cause severe persistent hypertension.
## Monitoring
* **Hemodynamics:** Continuous ECG, blood pressure monitoring (arterial line preferred for titration), central venous pressure (CVP), pulmonary artery pressures (if available).
* **Perfusion:** Urine output, peripheral pulses, capillary refill, mental status, lactate levels.
* **IV Site:** Frequent checks for signs of extravasation.
* **Metabolic:** Serum electrolytes, acid-base status.
## Clinical Pearls
* Norepinephrine is a first-line agent for septic shock.
* Administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, stop infusion and infiltrate the area with phentolamine.
* Titrate slowly to achieve desired hemodynamic effects while minimizing adverse events.
* Discontinuation should be gradual to avoid hypotension.
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*This information is intended for clinical professionals and does not replace comprehensive drug information resources. Always verify current prescribing information with the manufacturer's package insert or a trusted drug database.*
