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# Norepinephrine
## Overview
Norepinephrine is a potent vasopressor and inotropic agent. It stimulates alpha-1 adrenergic receptors, causing vasoconstriction and increasing peripheral vascular resistance. It also stimulates beta-1 adrenergic receptors in the heart, increasing heart rate and contractility.
## Primary Indications
* Severe hypotension (e.g., shock).
* Cardiogenic shock.
* Septic shock.
## Adult Dosing
* **Initial infusion rate:** 0.01 to 0.3 mcg/kg/min.
* **Titration:** Titrate to maintain target mean arterial pressure (MAP), typically 65 mmHg or higher.
* **Maximum dose:** Doses greater than 1 mcg/kg/min are generally not recommended without careful consideration due to increased risk of adverse effects.
## Pediatric Dosing
* **Initial infusion rate:** 0.05 to 0.1 mcg/kg/min.
* **Titration:** Titrate to maintain target MAP (e.g., age-adjusted target MAP). Dosing is highly individualized and often guided by local protocols and patient response.
* **Maximum dose:** Doses up to 1 mcg/kg/min may be used, and higher doses are sometimes required, but with increased caution.
## Dose Adjustments
* **Hepatic or Renal Impairment:** No specific dose adjustments are typically recommended, as norepinephrine is primarily metabolized by the liver and kidneys but its administration is based on acute hemodynamic targets.
## Contraindications
* Hypersensitivity to norepinephrine.
* Severe hypotension with hypovolemia (unless used as a temporizing measure before fluid resuscitation).
## Adverse Effects
* **Cardiovascular:** Hypertension, bradycardia (reflex), arrhythmias, peripheral ischemia, extravasation (leading to tissue necrosis).
* **Central Nervous System:** Headache, anxiety, tremor.
* **Respiratory:** Dyspnea.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiate hypertensive crisis. Avoid concurrent use; if unavoidable, use extreme caution and reduced doses.
* **Tricyclic Antidepressants (TCAs):** Potentiate hypertensive effects.
* **Anesthetic Agents:** May increase myocardial irritability and risk of arrhythmias.
* **Beta-blockers:** May cause unopposed alpha-adrenergic stimulation, leading to severe hypertension.
## Monitoring
* **Hemodynamic Parameters:** Continuous blood pressure monitoring (arterial line preferred), heart rate, cardiac output (if available).
* **Infusion Site:** Frequent assessment for signs of extravasation.
* **Urine Output:** To assess renal perfusion.
* **Mental Status:** To assess cerebral perfusion.
## Clinical Pearls
* Norepinephrine should be administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis.
* If extravasation occurs, stop the infusion immediately and infiltrate the area with phentolamine (an alpha-blocker).
* Norepinephrine is often a first-line vasopressor in septic shock, especially when other agents like dopamine have failed or are contraindicated.
* The goal of therapy is to achieve adequate tissue perfusion, not just a specific blood pressure number.
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**Disclaimer:** This information is intended for healthcare professionals and does not replace comprehensive drug information resources. Always consult the most current prescribing information and institutional protocols before administering any medication.
