Theophylline
**Theophylline** is a methylxanthine bronchodilator used primarily in the management of small airway disease in dogs and cats. Beneficial effects include bronchodilation, enhanced mucociliary clearance, stimulation of the respiratory centre, increased sensitivity to PaCO2, increased diaphragmatic contractility, stabilization of mast cells, and a mild inotropic effect. It also acts as a spasmolytic agent with mild diuretic action. > **Clinical Warning:** Theophylline has a **low therapeutic index** (therapeutic plasma values are 5-20 µg/ml). It must be dosed based on **lean body weight** to avoid toxicity.
Mecanismo: Causes inhibition of **phosphodiesterase** enzymes and antagonism of **adenosine** and prostaglandin receptors → increased intracellular cAMP → smooth muscle relaxation and **bronchodilation**. It also alters intracellular calcium and stimulates catecholamine release, providing mild inotropic and diuretic effects.
Dosificación por especie
- Bronchodilation · 20 mg/kg or 10-15 mg/kg · PO · q24h or q12h · Continuous · 20 mg/kg p.o. q24h or 10 mg/kg p.o. q12h which may be increased to 15 mg/kg p.o. q12h if no side effects on lower dose. Manufacturer only recommends q24h dosing. Some texts indicate q12h dosing of the sustained-release preparation is required to maintain therapeutic serum levels.
- Bronchodilation · 15-19 mg/kg · PO · q24h · Continuous · Sustained-release preparation.
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- Patients with a known history of arrhythmias
- Patients with a known history of seizures
Efectos adversos
- Vomiting
- Diarrhoea
- Polydipsia
- Polyuria
- Reduced appetite
- Tachycardia
- Arrhythmias
- Nausea
- Twitching
- Restlessness
- Agitation
- Excitement
- Convulsions
- Hyperaesthesia (cats)
Interacciones farmacológicas
- Cimetidine · May increase serum levels of theophylline · major
- Diltiazem · May increase serum levels of theophylline · moderate
- Erythromycin · May increase serum levels of theophylline · moderate
- Fluoroquinolones · May increase serum levels of theophylline · moderate
- Allopurinol · May increase serum levels of theophylline · moderate
- Phenobarbital · May decrease serum concentration of theophylline · moderate
- Pancuronium · Theophylline may decrease the effects of pancuronium · moderate
- Beta-adrenergic blockers (e.g., propranolol) · May antagonize each other's effects · moderate
- Halothane · Increased incidence of cardiac dysrhythmias · major
- Ketamine · Increased incidence of seizures · major
Monitoreo
- Serum theophylline concentrations (therapeutic target: 5-20 µg/ml)
- Heart rate and rhythm
- Clinical signs of toxicity (vomiting, agitation, seizures)
Sobredosis
**Clinical Pearl:** Overdose leads to severe arrhythmias, seizures, vomiting, and hypokalemia. Treatment is supportive: perform gastric decontamination if ingestion was recent, control seizures with diazepam or phenobarbital, treat arrhythmias as indicated, and monitor electrolytes closely.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.