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# Norepinephrine ## Overview Norepinephrine is a potent catecholamine acting primarily on alpha-1 adrenergic receptors (vasoconstriction) and, to a lesser extent, beta-1 receptors (inotropic effect). It is the first-line vasopressor for distributive shock. ## Primary Indications * Hypotension or shock (septic, cardiogenic, vasodilatory) refractory to fluid resuscitation. * Cardiac arrest (as an adjunct). ## Adult Dosing * **Initial Infusion:** 0.01–0.05 mcg/kg/min (or fixed starting rate of 2–5 mcg/min). * **Titration:** Titrate by 0.01–0.05 mcg/kg/min every 3–5 minutes based on hemodynamic response (typically MAP goal ≥ 65 mmHg). * **Maintenance:** Generally 0.05–0.5 mcg/kg/min. Doses exceeding 1 mcg/kg/min are considered high-dose and carry increased risk of end-organ ischemia. * **Note:** Always verify specific titration protocols per institutional guidelines. ## Pediatric Dosing * **Initial Infusion:** 0.05–0.1 mcg/kg/min. * **Titration:** Increase in increments of 0.05–0.1 mcg/kg/min as needed. * **Maximum:** Generally 1 mcg/kg/min. ## Dose Adjustments * **Hepatic/Renal Impairment:** No standard dose adjustment required; however, use with caution due to risk of microvascular ischemia. * **Weaning:** Taper slowly while monitoring blood pressure to prevent rebound hypotension. ## Contraindications * Hypersensitivity to norepinephrine. * Hypotension due to uncorrected blood volume deficit (except as an emergency measure to maintain coronary/cerebral perfusion). * Mesenteric or peripheral vascular thrombosis. ## Adverse Effects * **Cardiovascular:** Hypertension, arrhythmias (tachycardia, bradycardia), myocardial ischemia. * **Local:** Extravasation can lead to tissue necrosis/sloughing. * **Metabolic:** Lactic acidosis (secondary to peripheral vasoconstriction/hypoperfusion). ## Key Drug Interactions * **MAO Inhibitors/Tricyclic Antidepressants:** May cause severe, prolonged hypertensive crises. * **Beta-Blockers:** May lead to unopposed alpha-adrenergic vasoconstriction (severe hypertension). * **General Anesthetics (e.g., Cyclopropane, Halothane):** May sensitize the myocardium to catecholamines, increasing arrhythmia risk. ## Monitoring * **Hemodynamics:** Continuous ECG, arterial line blood pressure monitoring is strongly recommended. * **Lactate:** To assess for peripheral hypoperfusion. * **IV Site:** Ensure patency; if extravasation occurs, administer phentolamine into the infiltrated area immediately. ## Clinical Pearls * **Central Line:** Always prioritize central venous access for administration to minimize the risk of extravasation injury. * **Drug Compatibility:** Norepinephrine is chemically incompatible with alkaline solutions (e.g., sodium bicarbonate). * **Tachyphylaxis:** May occur with prolonged use; monitor for decreasing responsiveness. *** *Disclaimer: This information is for educational purposes only. Clinical dosing requirements vary based on patient-specific factors, institutional policy, and recent literature updates. Always consult your facility's current clinical guidelines and the official product monograph before prescribing or administering medication.*