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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 systemic vascular resistance and blood pressure. It also has some beta-1 adrenergic receptor activity, which can increase cardiac output.
## Primary Indications
* Treatment of severe hypotension, particularly in the context of shock (e.g., septic shock, cardiogenic shock).
* Restoration and maintenance of blood pressure.
## Adult Dosing
* **Starting Dose:** 0.01 to 0.05 mcg/kg/minute IV infusion.
* **Titration:** Increase dose by 0.005 to 0.01 mcg/kg/minute every 5-10 minutes as needed to achieve target blood pressure.
* **Maximum Dose:** Typically 0.3 mcg/kg/minute IV infusion, though higher doses may be used in refractory hypotension under close supervision.
Dosing is highly individualized based on patient response and is often guided by local institutional protocols and hemodynamic monitoring.
## Pediatric Dosing
* **Starting Dose:** 0.05 to 0.1 mcg/kg/minute IV infusion.
* **Titration:** Increase dose by 0.05 to 0.1 mcg/kg/minute every 5-10 minutes as needed.
* **Maximum Dose:** Up to 2 mcg/kg/minute IV infusion may be required, but target the lowest effective dose.
Dosing should be adjusted based on clinical assessment and hemodynamic response.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment; however, reduced clearance is possible. Close monitoring is essential.
* **Hepatic Impairment:** No specific dose adjustment; however, reduced clearance is possible. Close monitoring is essential.
## Contraindications
* Hypersensitivity to norepinephrine.
* Should not be used as the primary agent for hypotension due to blood volume deficits until volume has been adequately replaced.
* Use with extreme caution in patients with mesenteric or peripheral vascular thrombosis, as it may increase myocardial oxygen demand and exacerbate ischemia.
## Adverse Effects
* **Cardiovascular:** Arrhythmias (especially ventricular), bradycardia (reflex), hypertension, decreased cardiac output, peripheral ischemia, gangrene (with prolonged administration or extravasation).
* **Central Nervous System:** Headache, anxiety, dizziness, tremor.
* **Respiratory:** Dyspnea.
* **Other:** Extravasation leading to tissue necrosis.
## Key Drug Interactions
* **General Anesthetics:** May increase risk of arrhythmias.
* **Beta-blockers:** Can block the beta-1 effects of norepinephrine, potentially leading to unopposed alpha-1 vasoconstriction and severe hypertension.
* **MAO Inhibitors and Tricyclic Antidepressants:** May prolong and intensify the pressor effects of norepinephrine.
* **Oxytocic Drugs:** May cause severe sustained hypertension.
* **Alpha-blockers:** May reduce the pressor effects.
## Monitoring
* **Hemodynamics:** Continuous blood pressure monitoring (intra-arterial preferred), heart rate, cardiac rhythm.
* **Urine Output:** Monitor for adequate renal perfusion.
* **Extremities:** Assess for signs of peripheral ischemia (color, temperature, capillary refill).
* **Infusion Site:** Monitor closely for signs of extravasation.
## Clinical Pearls
* Always dilute norepinephrine in a compatible IV fluid before administration.
* Administer via a central venous catheter whenever possible to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, immediately stop the infusion, aspirate any residual drug, and infiltrate the area with phentolamine (per local protocol).
* Titrate infusion to achieve the lowest effective dose that maintains adequate tissue perfusion and vital organ function, not just a specific blood pressure number.
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*This information is intended for healthcare professionals. Please refer to the current prescribing information and consult with a pharmacist or physician for specific patient care decisions.*
