- Presents as a clear, 1mg/ml solution for intravenous infusion to treat severe bradycardia associated with AVN block or β-blockers (0.5 - 10μg/min)
- Although it also comes as a MDI for inhaled use it is no longer used to treat reversible airway obstruction as it was associated with an increased mortality
Isoprenaline
Isoprenaline
- Also known as isoproterenol, isoprenaline is a highly potent synthetic catecholamine with actions at β1 and β2 adrenoreceptors
Absorption
- Well absorbed orally but extensive 1st-pass metabolism by hepatic COMT means low oral bioavailability
Excretion
- Excreted as both unchanged isoprenaline and inactive conjugate metabolites in the urine
Respiratory
- Potent bronchodilator
- Inhibits histamine release in the lungs (increases mucus flow)
- Increases anatomical dead space and V/Q mismatch so may cause systemic hypoxaemia
Cardiovascular
- Positive chronotropy and inotropy, automaticity and cardiac output (β1 - effect)
- Tachycardia may decrease myocardial oxygen delivery
- Reduced SVR and therefore reduced MAP (β2 - effect)
- Reduced DBP reduces coronary perfusion pressure although some coronary vasodilation occurs
- Increases mesenteric and renal blood flow
Neurological
- No CNS effects
Gastrointestinal
- Leads to raised blood glucose and free fatty acid levels due to beta-effects