metaraminol tartrate: clinical use

Prescribing considerations

• Confirm and address reduced circulating volume where this is the main cause of hypotension; vasoconstriction can otherwise perpetuate inadequate tissue perfusion.
• Response is variable and cumulative pressor effects may persist after administration stops.
• Use particular caution in older people and in patients with heart disease, hypertension, thyroid disease, diabetes, cirrhosis or a history of malaria.
• The selected product should not be used in children younger than 12 years.
• Choose an appropriate large vein where possible, especially in patients with peripheral vascular disease or impaired peripheral circulation.

Contraindications and cautions

• Hypersensitivity to metaraminol or any excipient.
• Concurrent cyclopropane or halothane anaesthesia should be avoided unless the clinical circumstances demand otherwise.

Monitoring

• Continuous or comprehensive haemodynamic monitoring, including blood pressure and heart rhythm.
• Clinical response and signs of excessive hypertension, arrhythmia or pulmonary oedema.
• Peripheral perfusion and the injection site for extravasation or tissue ischaemia.
• Adequacy of circulating volume; consider electrolyte monitoring in cirrhosis if diuresis occurs.

Clinical pharmacology

Metaraminol has direct and indirect adrenergic activity, predominantly alpha-mediated vasoconstriction, with weaker beta-mediated positive inotropic effects. It displaces noradrenaline from neuronal stores, inhibits its uptake and can act as a false transmitter; direct intravenous administration has a rapid onset and a more prolonged action than noradrenaline.

Formulation and product differences

• The selected pre-filled syringe is already diluted and intended for direct intravenous injection only.
• It must not be diluted, mixed with other medicines, added to infusion fluids or used in a syringe pump driver.
• It contains sodium chloride, hydrochloric acid and water for injections; unlike some other metaraminol presentations, sodium metabisulfite is not listed as an excipient.
• The unopened syringe remains in its blister until use, must not be frozen and is discarded after single-patient use.

Injection

Route: Parenteral

Strengths: 0.5 mg/mL, 10 mg/mL