Elimination kinetics and protein binding of theophylline in the rabbit

The detailed elimination kinetics of theophylline were studied in 27 rabbits. Each received a 10 mg/kg intravenous bolus of aminophylline. The theophylline half-life ($\text{T}\text{1}\text{2}$) was 3.8 ± 0.63 hr. The apparent volume of distribution (V_D) and total body clearance (TBC) for theophylline were 439 ± 60 ml/kg and 81.0 ± 17.3 ml/kg·hr respectively. Theophylline protein binding was determined in 10 animals. The mean bound fraction was 74.3 ± 3.9% (range, 68.3–78.0%); the fraction bound was concentration indifferent over a serum concentration range of 5–20 μgm/ml.