Isoproterenol
**Isoproterenol** is a potent, non-selective beta-adrenergic agonist used primarily in emergency veterinary medicine. Key clinical features include: * **Cardiac Support:** Used to treat severe bradyarrhythmias, such as complete AV block or sinoatrial arrest, by increasing heart rate and contractility. * **Bronchodilation:** Historically used for acute bronchial constriction, though largely replaced by more selective $\beta_2$ agonists (like terbutaline or albuterol) to avoid cardiac side effects. * **Shock/Heart Failure:** Occasionally used as adjunctive therapy, but its use is limited due to its strong arrhythmogenic potential and tendency to cause tachycardia. **Clinical Pearl:** Because of its profound cardiostimulatory properties and the availability of safer, more targeted therapies (e.g., pacemakers for AV block, selective bronchodilators for asthma), isoproterenol is now infrequently used. It has a very short duration of action, meaning adverse effects dissipate quickly once the infusion is stopped.
Mecanismo: **Isoproterenol** is a synthetic sympathomimetic amine that acts as a potent, non-selective agonist at both **$\beta_1$** and **$\beta_2$ adrenergic receptors**, with virtually no $\alpha$-adrenergic activity. **Mechanism Pathway:** Drug binds to **$\beta_1$ and $\beta_2$ receptors** → activates **Gs-proteins** → stimulates **adenylyl cyclase** → increases intracellular **cyclic-AMP (cAMP)** → activates **Protein Kinase A (PKA)**. * **Cardiac Effects ($\beta_1$):** Increased cAMP leads to increased intracellular calcium influx → **positive inotropy** (increased contractility) and **positive chronotropy** (increased heart rate and pacemaker discharge rate). * **Smooth Muscle Effects ($\beta_2$):** Increased cAMP inhibits myosin light-chain kinase (MLCK) → relaxation of bronchial smooth muscle (**bronchodilation**) and peripheral vasculature (**vasodilation**). * **Immunologic Effects:** Inhibits the antigen-mediated release of histamine and slow-releasing substance of anaphylaxis (SRS-A).
Dosificación por especie
- Sinoatrial arrest, sinus bradycardia, complete AV block · 0.4 mg in 250 mL D5W drip slowly to effect · IV · to effect
- Short-term bronchodilatation · Dilute 0.2 mg in 50 mL of saline and administer 0.4 micrograms/kg as an IV infusion, monitor heart rate continuously and discontinue when heart rate doubles. · IV · once · Effects may only last for an hour · ARCI UCGFS Class 2 Drug
- Sinoatrial arrest, sinus bradycardia, complete AV block · 0.4 mg in 250 mL D5W drip slowly to effect · IV · to effect
- Sinoatrial arrest, sinus bradycardia, complete AV block · Isuprel Glossets 5-10 mg · sublingual or rectal · q4-6h
- Sinoatrial arrest, sinus bradycardia, complete AV block · 0.04-0.08 micrograms/kg/min · IV · CRI · Infusion
- Sinoatrial arrest, sinus bradycardia, complete AV block · 0.1-0.2 mg · IM, SC · q4h
- Sinoatrial arrest, sinus bradycardia, complete AV block · 0.4 mg in 250 mL D5W slowly · IV · slowly
- Adjunctive treatment for bradycardia associated with calcium channel blocker overdose · Mix 0.4 mg in 250 mL of D5W and give via slow IV drip to effect. · IV · to effect · Alternative to atropine
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Tachycardias or AV block caused by cardiac glycoside (digoxin) intoxication
- Ventricular arrhythmias that do not require increased inotropic activity
Efectos adversos
- Tachycardia
- Ventricular arrhythmias (highly arrhythmogenic)
- Anxiety and excitability
- Tremors
- Headache
- Weakness
- Vomiting
Interacciones farmacológicas
- General Anesthetics (cyclopropane, halogenated hydrocarbons) · Increased risk of developing arrhythmias. Propranolol may be administered should these occur.
- Beta-Blockers · May antagonize isoproterenol's cardiac, bronchodilating, and vasodilating effects. Can be used to treat isoproterenol-induced tachycardia, but use with caution in bronchospastic disease.
- Digoxin (Digitalis glycosides) · Increased risk of arrhythmias.
- Oxytocic Agents · Hypertension may result if used concurrently.
- Other Sympathomimetic Agents (e.g., phenylpropanolamine) · Should not be administered concurrently as increased toxicity may result.
- Theophylline · May increase the risk for theophylline toxicity.
Monitorización
- Cardiac rate and rhythm (ECG continuous monitoring highly recommended)
- Respiratory rate and auscultation (especially during anaphylaxis)
- Blood pressure
- Blood gases (if indicated and possible)
- Urine flow (if possible)
Sobredosis
High doses may cause an initial **hypertension**, followed by **hypotension**, as well as severe **tachycardias and other arrhythmias**. **Treatment:** * Halt or reduce the drug infusion (effects dissipate rapidly due to short half-life). * Provide supportive care. * If tachycardias persist, a **beta-blocker** could be considered for treatment, provided the patient does not have a bronchospastic disease.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.