II. Pathophysiology
- Synthetic Sympathomimetic amine
- Pure Beta Adrenergic Agonist
- Potent Chronotropic effects (b1)
- Increases Heart Rate (more than Epinephrine)
- Potentiates AV conduction
- Potent Inotropic effects (b1)
- Increases cardiac contractility
- Markedly increases Cardiac Output
- Potent peripheral vasodilatation (b2)
- Decreases Diastolic pressure and mean arterial pressure
- Bronchodilation (b2)
- Endocrine
- Increased Serum Glucose via glycogenolysis and Gluconeogenesis (b2)
- Increased fat breakdown via lipolysis of Triglycerides (b1)
- Other
- Decreased intestinal tone and motility
- Decreases Mast Cell release
- Potent Chronotropic effects (b1)
- Markedly increases myocardial oxygen demand (b1)
- May provoke Myocardial Ischemia
- May decrease coronary perfusion
III. Pharmacokinetics
- Very short Half-Life (<1.5 minutes)
- As with other Catecholamines, rapid metabolism by COMT (but minimal metabolism by MAO)
IV. Indications
- Other inotropic agents preferred over Isoproterenol
- Hemodynamically significant Bradycardia (pulse present)
- Specific Uses
- Heart Block
- Bradycardia in denervated transplanted heart
- Unresponsive to other measures
- Atropine
- Epinephrine
- Transcutaneous Pacing or transvenous pacing
- Dopamine
- Specific Uses
V. Contraindication
VI. Dosing: Pediatric Infusion (Same as Epinephrine preparation)
- Preparation
- Draw up "x" mg of Isoproterenol
- Where "x" = 0.6 x Weight in Kilograms
- Add enough D5W or NS for 100 ml total
- At this dilution:
- Infusion rate of 1 ml/h provides 0.1 ug/kg/min
- Start Dose: 10 ml/hour (10 ug/kg/min)
- Titrate to clinical response, adjusting every 5 min
VII. Dosing: Adult Infusion
- Preparation
- Dissolve 1 mg Isoproterenol in 250 ml D5W
- Final Concentration: 4 ug/ml
- Start Dose: 2 ug/min
- Titrate: 2-10 ug/min to clinical response
- Heart Rate over 60 beats per minute
VIII. Precautions
- Decreases Diastolic Blood Pressure
- No alpha adrenergic effect
- Increases Heart Rate (less diastolic filling time)
- May precipitate Myocardial Ischemia
- Increases myocardial oxygen demand
- Decreases coronary perfusion
- Induces Arrhythmias
- Exacerbates tachyarrhythmias due to Digitalis Toxicity
- Precipitates Hypokalemia
IX. References
- Olson (2020) Clinical Pharmacology, Medmasters, Miami, p. 13-33
- Goldstein (2010) Clin Auton Res 20(6):331-52 +PMID: 20623313 [PubMed]