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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 increasing blood pressure. It also has some beta-1 adrenergic effects, increasing heart rate and contractility.
## Primary Indications
* Treatment of hypotension in shock, particularly septic shock and cardiogenic shock.
## Adult Dosing
* **Continuous Intravenous Infusion:** Typically started at 0.01 to 0.02 mcg/kg/min.
* **Titration:** Titrate to achieve target mean arterial pressure (MAP) of 65 mmHg or higher, or to restore adequate tissue perfusion. Doses can be increased incrementally, often in steps of 0.01 to 0.02 mcg/kg/min every 5-15 minutes, up to a maximum of 0.3 mcg/kg/min. Some protocols may use higher doses in refractory shock.
## Pediatric Dosing
* **Continuous Intravenous Infusion:** Typically started at 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate to achieve target MAP greater than or equal to the gestational age plus 2 mmHg in neonates, or greater than or equal to 50 mmHg in infants and children, or to restore adequate tissue perfusion. Doses can be increased incrementally, often in steps of 0.05 to 0.1 mcg/kg/min every 5-15 minutes, up to a maximum of 1-2 mcg/kg/min. Exact titration parameters are often guided by local pediatric critical care protocols.
## Dose Adjustments
* No specific dose adjustments are typically required for hepatic or renal impairment, as the drug is extensively metabolized and its effects are titratable.
## Contraindications
* Hypersensitivity to norepinephrine.
* Concurrent use of certain anesthetic agents (e.g., cyclopropane, halothane) due to risk of severe hypertension and arrhythmias.
## Adverse Effects
* **Cardiovascular:** Hypertensive crisis, reflex bradycardia, arrhythmias (including ventricular), peripheral ischemia, extravasation leading to tissue necrosis.
* **Other:** Headache, anxiety, dizziness, dyspnea, tremor.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** May potentiate the pressor response and prolong the duration of action. Avoid concurrent use or use with extreme caution and significantly reduced doses.
* **Tricyclic Antidepressants (TCAs):** May potentiate the pressor response.
* **Beta-blockers:** May cause unopposed alpha-stimulation leading to severe hypertension.
* **Ergot alkaloids:** May enhance pressor effects.
* **General anesthetics (volatile):** Increased risk of arrhythmias and hypertension.
## Monitoring
* Continuous hemodynamic monitoring (arterial blood pressure, central venous pressure, cardiac output if available).
* Heart rate and rhythm.
* Urine output.
* Peripheral perfusion (skin temperature, capillary refill).
* Infusion site for signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically reconstituted and further diluted in a compatible IV solution (e.g., D5W, Normal Saline). Follow institutional guidelines for preparation and dilution.
* Administer via a central venous catheter to minimize risk of extravasation and tissue necrosis.
* If extravasation occurs, stop the infusion, aspirate any residual drug, and infiltrate the affected area with phentolamine (e.g., 5-10 mg in 10-15 mL saline) to counteract vasoconstriction.
* Taper the infusion gradually to avoid sudden hypotension.
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**Disclaimer:** This information is intended for healthcare professionals and does not substitute for comprehensive drug information resources. Always verify current prescribing information, including indications, contraindications, warnings, precautions, and adverse reactions, with the most up-to-date product labeling and institutional protocols.
