isoproterenol

Introduction

Tradename: Isuprel.

Indications

• severe, unresponsive bronchospasm (not 1st or 2nd line agent)
• temporary management of torsades de pointes
• hemodynamically significant bradycardia in denervated & transplanted hearts
• temporary use in 3rd degree AV heart block until insertion of pacemaker
• unresponsive cardiac shock

Dosage

• must be diluted
• cardiac arrhythmias
  • 0.02-0.06 mg (0.1-0.3 mL of 1:5000 dilution) IV bolus
  • followed by IV saline bolus
  • infusion of 5-20 ug/min (1 mg in 500 mL = 2 ug/mL)
• shock: infusion of 0.5-5 ug/min titrated to response

Injection: 0.2 mg/mL [1:5000] (5 mL)

Pharmacokinetics

• rapid onset of action
• metabolized by tissues, GI tract, liver, lungs
• duration of action approximately 1 hour

elimination via liver

elimination via kidney

Adverse effects

• common (> 10%)
  • discoloration of saliva (pinkish-red), insomnia, restlessness, dry mouth or throat
• less common (1-10%)
  • weakness, nausea/vomiting, trembling, hypertension, increased sweating, tachycardia, flushing of face, dizziness, lightheadedness
• uncommon (< 1%)
  • paradoxical bronchospasm, arrhythmias, chest pain
• other
  • ventricular ectopy
  • tachycardia
  • hypotension
  • headache
  • angina
  • anxiety
  • agitation
  • flushing

• drug adverse effects of adrenergic receptor agonists
• drug adverse effects of beta-adrenergic receptor agonists
• drug adverse effects of sympathomimetic(s)

Drug interactions

• beta blockers antagonize the effects of isoproterenol
• general anesthetics in combination increase cardiac irritability
• theophylline in combination increases cardiac toxicity

Mechanism of action

• directly stimulated beta-1 & beta-2 adrenergic receptors
• cardiac effects
  • positive inotrope
  • increases cardiac output by increasing contractility & stroke volume
  • increases myocardial consumption of O2
  • decreases cardiac efficiency
  • shortens conduction time & refractory period of the AV node
  • decreases afterload
  • increases preload
  • increases systolic blood pressure
• other effects (mainly beta-2 adrenergic effects)
  • relaxation of the bronchial tree
  • peripheral vasodilation
  • relaxes GI & uterine smooth muscle
  • inhibits slow-releasing substance of anaphylaxis
  • inhibits histamine release
  • CNS stimulation
  • glycogenolysis
  • stimulates insulin release (unlike epinephrine)

More general terms

• catecholamine
• beta-adrenergic receptor agonist
• ethanolamine

Component of

• isoproterenol/phenylephrine
• ca+2/iodine/isoproterenol

Database

• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=3779
• PubChem: http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=5808