Theophylline In Dogs & Cats: Uses, Dosage and Side Effects
Overview
- Causes inhibition of phosphodiesterase, alteration of intracellular calcium, release of catecholamine, and antagonism of adenosine and prostaglandin.
- Results in bronchodilation and other effects.
- Functions as a spasmolytic agent and has a mild diuretic action.
Uses of Theophylline
- Employed in the treatment of small airway disease.
- Beneficial effects encompass bronchodilation, enhanced mucociliary clearance, stimulation of the respiratory center, increased sensitivity to PaCO2, heightened diaphragmatic contractility, stabilization of mast cells, and a mild inotropic effect.
Dose of Theophylline in Dogs and Cats
Dogs:
- Bronchodilation: 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 (NB: manufacturer only recommends q24h dosing).
- Some texts indicate q12h dosing of the sustained-release preparation is required to maintain therapeutic serum levels.
Cats:
- Bronchodilation: 15–19 mg/kg p.o. q24h (sustained-release preparation).
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Side Effects of Theophylline in Dogs and Cats
- Adverse effects may include vomiting, diarrhoea, polydipsia, polyuria, reduced appetite, tachycardia, arrhythmias, nausea, twitching, restlessness, agitation, excitement, and convulsions.
- Cats may exhibit hyperaesthesia.
- Most adverse effects correlate with serum levels and may indicate toxic concentrations.
- The severity of these effects can be mitigated with modified-release preparations, but they are more likely with frequent administration.
Contraindications of Theophylline in Dogs and Cats
- Patients with a known history of arrhythmias or seizures.
Some Notes:
- Agents that can increase the serum levels of theophylline include cimetidine, diltiazem, erythromycin, fluoroquinolones, and allopurinol.
- Phenobarbital may decrease the serum concentration of theophylline.
- Theophylline may diminish the effects of pancuronium.
- Theophylline and beta-adrenergic blockers (e.g., propranolol) may counteract each other’s effects.
- Administering theophylline with halothane may lead to an increased incidence of cardiac dysrhythmias, and with ketamine, an increased incidence of seizures.
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