Pharm 101: Adrenaline

Class

Endogenous catecholamine
Vasopressor

Pharmacodynamics

• Alpha and beta agonist
  • Beta 1 = positive inotropy and chronotropy
  • Alpha = vasoconstriction
  • Beta 2 = skeletal muscle vasodilation, may explain decreased DBP sometimes seen
• Non-selective adrenergic agonist:
  • Potent beta-1 receptor activity causes positive inotropy and chronotropy
  • Moderate alpha-1 receptor activity causes peripheral vasoconstriction and increases SVR
  • Moderate beta-2 receptor activity causes skeletal muscle vasodilation (may explain decreased DBP sometimes seen), and relaxes bronchial smooth muscle and stabilises mast cells

Pharmacokinetics

• IV/IM/ETT/SC administration
• Onset of action 1-2 minutes
• Half-life 5 minutes
• Duration of action 2-10 minutes
• Metabolised by MAO and COMT to VMA and metadrenaline
• Urinary excretin of metabolites

Clinical uses

• To increase CO/HR, MAP and coronary blood flow
• Septic shock:
  • In addition to noradrenaline (first line agent) to raise MAP
• Cardiac arrest
• Anaphylaxis
• Bronchospasm causing respiratory distress
• Infusion (central):
  • 6mg adrenaline in 100ml 5% dextrose (final concentration 60 microg/ml)
  • 1ml/hr = 1 microg/min
  • Starting dose: 1-4 microg/min, titrate to BP
  • Usual dose range: 1-20 microg/min

Adverse effects

• Angina, tachycardia, arrhythmias and palpitations
• Tissue ischaemia or necrosis due to vasoconstriction
• Hyperglycaemia
• Lactic acidosis

Precautions/contraindications

• Hypotension due to uncorrected hypovolaemia
• Tachycardia and arrhythmias
• Hypersensitivity to sulphites
• Wean gradually to avoid hypotension

Further reading

• Nickson C. Initial Management of Sepsis. LITFL

References

• Katzung BG. Basic & Clinical Pharmacology. 14e. 2018: 96-97
• Better Safe Care. Melbourne, Australia: Victorian Agency for Health Information; 2018. Adrenaline (epinephrine). 2019 May 07 [cited 2020 Aug 02].