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# Norepinephrine
## Overview
Norepinephrine is a potent catecholamine with primary alpha-1 adrenergic agonist activity (vasoconstriction) and moderate beta-1 adrenergic agonist activity (inotropic effect). It is the first-line vasopressor for septic shock.
## Primary Indications
* Acute hypotension (septic, cardiogenic, or vasodilatory shock).
* Adjunct treatment during cardiac arrest.
## Adult Dosing
* **Initial:** Start at 0.01–0.05 mcg/kg/min or 5–10 mcg/min (fixed rate).
* **Titration:** Titrate by 0.05–0.1 mcg/kg/min every 2–5 minutes to achieve target Mean Arterial Pressure (MAP), typically ≥65 mmHg.
* **Maintenance:** Usual range is 0.01–3 mcg/kg/min.
* **Max:** No absolute maximum dose; however, doses exceeding 0.5 mcg/kg/min often require the addition of a second vasopressor (e.g., vasopressin).
## Pediatric Dosing
* **Initial:** 0.05–0.1 mcg/kg/min.
* **Titration:** Titrate in increments of 0.05–0.1 mcg/kg/min to target blood pressure.
* **Max:** Generally considered up to 1–2 mcg/kg/min depending on clinical setting and institutional protocols.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No specific dosage adjustments established.
* **Geriatric:** Use the lowest effective dose; monitor for increased risk of tachyarrhythmias and myocardial ischemia.
## Contraindications
* Hypersensitivity to norepinephrine.
* Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary and cerebral perfusion until fluid replacement is complete).
## Adverse Effects
* **Cardiovascular:** Tachycardia, bradycardia (reflex), arrhythmias, hypertension, myocardial ischemia.
* **Extravasation:** Tissue necrosis and sloughing due to intense vasoconstriction.
* **Local:** Injection site pain.
## Key Drug Interactions
* **MAO Inhibitors / TCAs:** May produce severe, prolonged hypertension due to inhibited metabolism/reuptake of amines.
* **Beta-blockers:** May cause excessive hypertension and paradoxical bradycardia due to unopposed alpha-adrenergic activity.
* **Anesthetics (Halogenated hydrocarbons):** May increase myocardial sensitivity to norepinephrine, predisposing to arrhythmias.
## Monitoring
* **Hemodynamics:** Continuous MAP monitoring via arterial line is strongly recommended.
* **Physical:** Monitor IV site for extravasation every hour; monitor distal extremity perfusion (coolness, mottling).
* **Cardiovascular:** Continuous ECG for heart rate and rhythm; monitor for signs of ischemia (ST-segment changes).
## Clinical Pearls
* **Extravasation Management:** If extravasation occurs, stop infusion, leave cannula in place, and attempt to aspirate surrounding drug. Administer **phentolamine** (5–10 mg in 10 mL saline) subcutaneously into the affected area to counteract vasoconstriction.
* **Administration:** Must be administered via a central venous catheter whenever possible to reduce the risk of infiltration.
* **Compatibility:** Must be diluted before administration (usually in D5W or D5W/NS). Norepinephrine may be inactivated by alkaline solutions.
* **Local Protocols:** Titration schedules and target MAP goals must be verified against current institutional practice guidelines.
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**Educational Disclaimer:** This information is for educational purposes only. Clinical practice standards can change. Always verify dosages, contraindications, and compatibility with your institution's latest policy, the drug manufacturer's package insert, or a reliable clinical decision support resource before prescribing or administering medication.
