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# Norepinephrine
## Overview
Norepinephrine (Levophed) is a potent alpha-adrenergic agonist with some beta-1 adrenergic activity. It primarily causes vasoconstriction, leading to increased systemic vascular resistance and blood pressure. It also has a positive inotropic effect on the heart.
## Primary Indications
* Management of severe hypotension and shock, particularly distributive shock (e.g., septic shock, neurogenic shock).
* Restoration of hemodynamic function in patients with sepsis.
## Adult Dosing
* **Usual Starting Dose:** 0.01 to 0.02 mcg/kg/minute IV infusion.
* **Titration:** Increase dose in increments of 0.01 to 0.02 mcg/kg/minute every 5-10 minutes to achieve target systolic blood pressure (SBP) of 80-110 mmHg or mean arterial pressure (MAP) of 65-75 mmHg, as per local protocol.
* **Maximum Dose:** Typically 1 mcg/kg/minute, though doses up to 3 mcg/kg/minute have been used in refractory cases.
## Pediatric Dosing
* **Usual Starting Dose:** 0.05 to 0.1 mcg/kg/minute IV infusion.
* **Titration:** Increase dose in increments of 0.05 to 0.1 mcg/kg/minute every 5-10 minutes to achieve target MAP of 50-70 mmHg or SBP 70-90 mmHg, as per local protocol.
* **Maximum Dose:** Typically 1-2 mcg/kg/minute, but higher doses may be required.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, as the drug is metabolized in the liver and tissues and excreted renally. However, careful titration is crucial in all patients.
## Contraindications
* Hypersensitivity to norepinephrine.
* Use as the sole agent to maintain blood pressure in patients with severe volemic shock prior to volume resuscitation.
* Use in patients with occlusive vascular diseases (e.g., peripheral vascular embolism, mesenteric vascular occlusion) unless the risk of death is imminent.
## Adverse Effects
* **Cardiovascular:** Hypertensive crisis, bradycardia (reflex), arrhythmias, chest pain, reduced cardiac output, peripheral ischemia, digital ischemia, extravasation leading to tissue necrosis.
* **Central Nervous System:** Headache, anxiety, dizziness.
* **Other:** Tremor, sweating.
## Key Drug Interactions
* **Monoamine Oxidase Inhibitors (MAOIs):** Potentiated pressor effect; avoid concurrent use or use extreme caution with reduced doses.
* **Tricyclic Antidepressants (TCAs):** Potentiated pressor effect; use with caution.
* **Ergot alkaloids, oxytocic drugs:** May cause severe prolonged hypertension.
* **Anesthetics:** May increase myocardial irritability and risk of arrhythmias.
* **Alpha-adrenergic blockers:** May antagonize the pressor effect.
* **Beta-adrenergic blockers:** May unmask alpha-adrenergic effects or cause unopposed alpha stimulation.
## Monitoring
* Continuous ECG monitoring.
* Frequent blood pressure monitoring (arterial line preferred for continuous infusions).
* Central venous pressure (CVP) and pulmonary artery pressures (if available).
* Urine output.
* Peripheral perfusion and skin temperature.
* Infusion site for signs of extravasation.
## Clinical Pearls
* Norepinephrine is typically administered via a central venous catheter to minimize the risk of extravasation and tissue necrosis. If peripheral administration is necessary, use a large vein and monitor the site meticulously.
* Phentolamine is the antidote for extravasation; inject subcutaneously into the affected area.
* Always ensure adequate volume status before or concurrently with norepinephrine initiation to avoid worsening tissue perfusion.
* The goal of therapy is not a specific blood pressure number but to restore adequate tissue perfusion.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the official prescribing information and relevant clinical guidelines for complete and up-to-date details before making any treatment decisions.*
