Metaraminol

Aka. Aramine, Metaradrine, Pressonex

CLASS

Sympathomimetic

INDICATIONS

• Hypotension secondary to reduced systemic vascular resistance (e.g. general anaesthetic / spinal anaesthesia)

ADMINISTRATION / DOSING

• Intravenous (IV) peripherally
• Usually prepared in a 0.5 mg / mL concentration, in 10 – 60 mL syringes
• Boluses:
  • Adults: 0.5 – 1 mg (1 – 2 mL of standard strength as above) every 1 – 2 min
  • Children: 5 – 10 microgs/kg every 1 – 2 min
• Infusion:
  • Adults: start at 0.05 mg/kg/h and titrate to effect every 1-2 min
  • Children: start at 5 microgs/kg/min and titrate to effect every 1-2 min
• With multiple boluses or an infusion, it is recommended to use an arterial line to assist with appropriate titration as well as continuous ECG monitoring
• Metaraminol is compatible with most IV fluids, check for drug specific incompatibilities, although it does include:
  • Atropine and furosemide. Check for other less frequently used medications.
• It is preferable to not use via Y-site as it may result in changed infusion rate if using as an infusion (this goes for all vasopressor/-dilator infusions)

MECHANISM OF ACTION

• Metaraminol is a synthetic sympathomimetic amine
• It has both direct and indirect alpha-1 adrenoreceptor agonist effects, resulting in peripheral vasoconstriction resulting in an increase in both systolic and diastolic blood pressure
• The indirect effects are mediated by increased noradrenaline release from storage vesicles
  • This is also hypothesised as to why tachyphylaxis can develop while using long duration infusions, or multiple boluses of metaraminol
• It is also proposed that metaraminol is an beta-1 agonist, however, it is noted that there is generally a reflex bradycardia with its use

PHARMACEUTICS

• Vial of 10 mg in 1 mL, pre-filled syringe with a concentration of 0.5 mg/mL (commonly a 6 mL syringe in Australia)
• Clear colourless solution
• Keep out of direct light
• Keep below 25^oC
• Infusion stable for up to 24 hours
• Excipients include: sodium chloride and sodium metabisulfite

PHARMACOKINETICS

• Pharmacokinetic data are limited
• Absorption
  • Oral bioavailability is about 15-20% (although the oral route is not recommended)
  • IV onset after 1 – 2 min
• Distribution
  • Limited information
• Metabolism
  • Metabolism in the liver (although does not need dose adjustment in hepatic failure)
• Elimination
  • T_1/2 = 20 – 60 min
  • Renal mostly as metabolites (does not need dose adjustment in renal failure), and bile as metabolites

PHARMACODYNAMICS

• CNS:
  • Headache, restlessness
• CVS:
  • Vasopressor agent resulting in an increase in systolic and diastolic blood pressure
  • Theoretically a positive inotrope, more commonly seen is a reflex bradycardia with associated rise in blood pressure.
• GIT:
  • Nausea
  • Redistribution of splanchnic blood flow
• SKIN:
  • While a theoretical risk, necrosis from extravasation is essentially unheard of (if you want a deep dive on metaraminol, see Alex Yartsev’s Deranged Physiology)
• OTHER:
  • Redistribution of muscular blood flow

CONTRAINDICATIONS

• Hypersensitivity to sulfites
• Concomitant use of halothane or cyclopropane anaesthesia

CHEMICAL STRUCTURE

References and Links

References

• Australian Injectable Drugs Handbook, 8th Edition. (2025). Retrieved 04 May 2025, from https://aidh.hcn.com.au/
• Australian Medicines Handbook. (2025). Retrieved 04 May 2025, from https://amhonline.amh.net.au/
• IBM Micromedex. (2025). Retrieved 04 May 2025, from https://www.micromedexsolutions.com
• eMIMS Elite (2025). Retrieved 04 May 2025, from https://app.emimselite.com.acs.hcn.com.au

FOAMED

• Deranged Physiology section on Metaraminol

Cite this article as: Pearlman, J. (2025, May 05). Metaraminol. Life in the Fast Lane. https://litfl.com/metaraminol/