07/04/2025
Metaraminol
Uses:
🔹 Management of Hypotension:
• Short-term treatment of hypotension secondary to epidural or spinal anesthesia.
• Perioperative hypotension management in surgical settings.
• Emergency treatment of acute hypotension episodes.
🔹 Treatment of Shock States:
• Bridge therapy in cardiogenic or septic shock before definitive management.
🔹 Cesarean Section:
• Management of hypotension during cesarean sections, particularly after spinal anesthesia.
Dose:
🔹 Adult:
• Bolus: 0.5–1 mg (1–2 mL of 0.5 mg/mL solution) intravenously, repeated as necessary.
• Infusion: 0.1–0.5 mg/min, titrated to achieve desired blood pressure.
• Maximum Dose:
• Bolus: 5 mg per administration.
• Infusion: Up to 20 mL/hour (100 mcg/mL solution).
🔹 Paediatric:
• Bolus: 0.05–0.1 mg/kg intravenously.
• Infusion: Start at 0.1 mcg/kg/min and titrate to response.
• Maximum Dose:
• Bolus: 0.5 mg/kg per administration.
• Infusion: Up to 0.5 mcg/kg/min.
🔹 Geriatric:
• Start at lower doses (bolus: 0.25–0.5 mg, infusion: 0.1 mg/min).
🔹 Severe Renal Impairment:
• Consider a 25–50% dose reduction.
Presentation:
🔹 Parenteral:
• Ampoules containing 10 mg/1 mL or 2.5 mg/5 mL.
• Standard preparation: 20 mg diluted with 38 mL of normal saline (0.5 mg/mL).
🔹 Brand Name:
• Aramine
Notes:
🔹 Drug Class:
• Synthetic sympathomimetic amine and alpha-1 adrenergic agonist.
🔹 Mechanism of Action:
• Direct Effects: Alpha-1 adrenergic receptor activation causing peripheral vasoconstriction, increasing systemic vascular resistance.
• Indirect Effects: Weak stimulation of norepinephrine release.
• Effects: Positive inotropic effect and minimal cardiac output changes unless reflex bradycardia occurs.
🔹 Pharmacokinetics:
• Onset: Immediate with IV bolus.
• Duration: 20–60 minutes for bolus doses.
• Volume of Distribution: 0.3–0.4 L/kg.
• Half-Life: 30–40 minutes.
• Metabolism and Elimination: Minimal hepatic metabolism; renal excretion as unchanged drug and metabolites.
🔹 Adverse Effects:
Common:
• Reflex bradycardia, pulmonary edema, reduced renal perfusion, and site irritation.
Rare:
• Arrhythmias, digital/peripheral ischemia, and coronary artery spasm.
Serious:
• Extravasation leading to tissue necrosis and hypertensive crisis with MAOI interaction.
🔹 Contraindications:
Absolute:
• Hypersensitivity, hypertrophic obstructive cardiomyopathy, Prinzmetal’s angina, pheochromocytoma.
Relative:
• Peripheral vascular disease, first trimester of pregnancy, concurrent use of MAOIs.
🔹 Drug Interactions:
• Enhanced effects with MAOIs and tricyclic antidepressants.
• Increased arrhythmia risk with halogenated anesthetics.
• Reduced effectiveness with calcium channel blockers.
🔹 Special Considerations:
• Extravasation: Manage with phentolamine infiltration.
• Monitoring: Continuous BP and urine output monitoring during use.
• Switch to Norepinephrine: If prolonged vasopressor therapy is required (>48 hours).
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