Pharmacokinetic studies of theophylline in dogs.

The pharmacokinetics of theophylline were investigated in dogs following intravenous, single oral, and multiple oral doses of aminophylline. Mean half-life (t1/2) of theophylline following single intravenous administration was 5.7 h and the apparent specific volume of distribution (V'd area) was 0.82 litre/kg. The bioavailability of theophylline was high (91%) following oral administration of aminophylline tablets and the absorption half-life (t1/2ab) was 0.4 h. Theophylline plasma concentrations observed following repeated oral administration of aminophylline tablets were somewhat greater than predicted. This suggests that theophylline plasma concentrations should be monitored and the dosage regimen individually adjusted in critically ill animals.