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# Norepinephrine
## Overview
Norepinephrine is a sympathomimetic amine that acts as a potent alpha-adrenergic agonist and a weaker beta-1 adrenergic agonist. It primarily causes vasoconstriction, leading to an increase in blood pressure and systemic vascular resistance.
## Primary Indications
* Severe hypotension and shock (e.g., septic shock, cardiogenic shock).
* To restore vascular tone in hypotensive states.
## Adult Dosing
* **Initiation:** Typically starts at 0.01 to 0.02 mcg/kg/min via continuous intravenous infusion.
* **Titration:** Titrate to achieve target mean arterial pressure (MAP), often 65 mmHg. Doses can range from 0.01 to 0.3 mcg/kg/min.
* **Maximum:** Doses higher than 0.3 mcg/kg/min are generally not recommended and may increase the risk of adverse effects without significant benefit. Some sources may suggest higher maximums based on extreme circumstances and clinician judgment.
## Pediatric Dosing
* **Initiation:** Typically 0.05 to 0.1 mcg/kg/min via continuous intravenous infusion.
* **Titration:** Titrate to achieve target MAP (e.g., target systolic blood pressure >70 mmHg plus 2 times the patient's age in years, or a specific target MAP based on institution/guideline). Doses can range from 0.05 to 2 mcg/kg/min.
* **Maximum:** Doses higher than 2 mcg/kg/min are generally not recommended.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment, but caution and close monitoring are warranted due to potential accumulation.
* **Hepatic Impairment:** No specific dose adjustment, but caution and close monitoring are warranted.
## Contraindications
* Hypersensitivity to norepinephrine.
* Certain patients during cyclopropane or halogenated hydrocarbon anesthesia (risk of severe hypertension and arrhythmias).
## Adverse Effects
* **Cardiovascular:** Hypertension, reflex bradycardia, arrhythmias, peripheral ischemia, necrosis (especially with extravasation).
* **Central Nervous System:** Headache, anxiety, dizziness.
* **Other:** Pallor, tremors.
## Key Drug Interactions
* **Anesthetics:** Increased risk of arrhythmias and hypertension with cyclopropane and halothane.
* **Beta-blockers:** May potentiate the pressor effect of norepinephrine.
* **MAO Inhibitors and Tricyclic Antidepressants:** Can prolong and intensify the pressor response; avoid concurrent use or use with extreme caution.
* **Oxytocic Agents:** May cause severe persistent hypertension.
* **Alpha-adrenergic Blockers:** May reduce the pressor effect.
## Monitoring
* Continuous blood pressure monitoring (arterial line preferred).
* Heart rate and rhythm.
* Urine output.
* Peripheral perfusion (skin color, temperature, capillary refill).
* Central venous pressure (if indicated).
* Signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, immediately stop the infusion, remove the IV catheter, and administer an alpha-adrenergic blocking agent (e.g., phentolamine) infiltrated into the affected area.
* Norepinephrine has a short half-life; effects diminish rapidly after discontinuation.
* Titrate to the lowest effective dose to achieve hemodynamic goals and minimize adverse effects.
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*Disclaimer: This information is for educational purposes only and does not constitute medical advice. Always verify current prescribing information with the official drug label and consult with a qualified healthcare professional before making any decisions related to patient care.*
