Absorption and dosage of theophylline in the horse after single and repeated administration of a microencapsulated preparation

Abstract

Summary The kinetics of 2 formulations of theophylline were studied in horses. In an initial cross‐over study (Phase I) serum concentration‐time curves were determined for granulated and microencapsulated theophylline after a single oral administration (5 mg/kg bwt). In Phase II microencapsulated theophylline was administered at 5 mg/kg bwt/12 h for 10 days at feeding time, as in normal clinical practice. Although no significant differences between the 2 preparations were found with respect to the main kinetic parameters, the microencapsulated form was more evenly and completely absorbed from the digestive tract; furthermore, after the repeated treatment, its trough‐peak serum concentrations were always within the therapeutic window and no toxic effects were observed in treated animals.

Theophylline does not potentiate the effects of a low dose of dexamethasone in horses with recurrent airway obstruction

“…Serum concentrations of theophylline between 28 and 55 µmol/l have been shown to potentiate the anti-inflammatory effects of corticosteroids in human asthmatics (Ito et al 2002). The dose and formulation of theophylline administered to horses in the present study were chosen to achieve these concentrations and were based on prior pharmacokinetic studies of the drug in horses (Button et al 1985;Ingvast-Larsson et al 1985;Goetz et al 1989;Roncada et al 1995). However, the targeted minimal serum concentration was achieved in all horses and theophylline alone did not improve lung function in horses with RAO with this 7 day treatment regimen.…”

“…Blood samples were drawn directly from a jugular vein in dry vacutainers 7 . Serum aliquots were obtained by centrifugation for 15 min at 1000 g and stored at -20ºC until assayed (Roncada et al 1995).…”

Systematic analysis to assess the scientific validity of the international residue limits for caffeine and theophylline in horse‐racing

“…For the calculation of the EPC, IPC and IUC for theophylline, shown in table 9, a dose of 5 mg/kg orally with a dosage interval of 12 hours was chosen. This dosage regimen equals a dose frequently recommended in the literature for bronchodilation in adult horses 17 18 . A generic safety factor of 1/500 was used to calculate the IPC from the EPC.…”