Isoproterenol (Isoprenaline) Half-Life
Isoproterenol has an elimination half-life of approximately 2-5 minutes when administered intravenously, making it an extremely short-acting agent that requires continuous infusion for sustained effect. 1
Pharmacokinetic Properties
The distribution half-life of isoproterenol is approximately 40 minutes, while the elimination half-life is 4.5 hours for the related compound treprostinil, but isoproterenol itself has a much shorter elimination half-life of 2-5 minutes. 1 This ultra-short half-life explains why isoproterenol must be administered as a continuous infusion rather than intermittent boluses for sustained chronotropic and inotropic effects. 1
Clinical Implications
The 2-5 minute half-life means that if an isoproterenol infusion is accidentally discontinued, the patient is at immediate risk for acute rebound deterioration, particularly in patients with severe bradycardia or pulmonary hypertension. 1
Physiological responses to isoproterenol reach greater than 90% of steady-state levels after approximately 8 minutes of continuous infusion, though plasma concentrations may not reach true steady state even after 40 minutes. 2
The cardiovascular and metabolic effects of isoproterenol largely resolve within a few minutes of discontinuing the infusion, consistent with its short half-life. 3
Dosing Context
For symptomatic bradycardia, isoproterenol is administered as 20-60 mcg IV bolus followed by doses of 10-20 mcg, or as a continuous infusion of 1-20 mcg/min based on heart rate response. 1
The short half-life necessitates careful titration and continuous monitoring, as effects dissipate rapidly upon cessation of infusion. 1
Important Distinction
- Isoproterenol's 2-5 minute half-life contrasts sharply with epoprostenol (another prostacyclin used in pulmonary hypertension), which also has a 2-5 minute half-life, and treprostinil, which has a 4.5-hour elimination half-life. 1