Pharm 101: Metaraminol

Class

Vasopressor

Pharmacodynamics

• Synthetic sympathomimetic
• Direct and indirect (via noradrenaline release) alpha 1 receptor agonist
• Organ system effects:
  • Vasoconstriction: increases SVR/PVR, increases BP
  • Reflex bradycardia
  • Cardiac output either unchanged or decreased
  • Indirect increase in coronary artery flow
  • Reduced blood flow to viscera, kidneys, skin

Pharmacokinetics

• IV administration
• Onset of action 1-2 minutes
• Duration of action 20-60 minutes
• Half-life: minutes

Clinical uses

• IV administration:
  • Bolus 0.5-2 mg
  • Infusion 0.5-10 mg/hr titrated to BP parameters
• Shock:
  • Temporising measure whilst other treatment instituted (fluids etc.)
• Sympathetic nervous system failure e.g. spinal injury or anaesthesia

Adverse effects

• Bradycardia (reflex)
• Arrhythmias

References

• Forrest P. Vasopressors. Royal Prince Alfred Hospital, Sydney, Australia.
• Better Safe Care Victoria. Clinical Guideline: Metaraminol. Melbourne, Australia.
• Katzung BG. Basic & Clinical Pharmacology. 14th ed. United States of America: McGraw-Hill Education; 2018. 149 p.