Pharmacokinetics of oral theophylline in Thai asthmatic children

Pharmacokinetic studies of theophylline were carried out in 12 Thai asthmatic children after oral administration of Elixir Quibron and Tablet Aminophylline. No significant differences in any of the pharmacokinetic parameters between these two dosage forms were observed. Peak serum concentrations of theophylline were reached in an average time of 3.16 hours (range 1.71-7.71). It was shown that the elimination half-life of theophylline in Thai asthmatic children (average 7.21 hours) was longer than that observed for subjects in western countries. Variations in elimination half-lives ranging from 4.44 to 14.34 hours were intersubject variations. Due to the slow elimination of theophylline in Thai patients, a dosage regimen of 5 mg/kg every 8 hours was recommended as more suitable than 5 mg/kg every 6 hours. Using data from this study, the predicted maximum and minimum serum theophylline concentrations at steady state were calculated to be 16.53 micrograms/ml and 9.96 micrograms/ml, respectively. This dosage regimen should be suitable not only for Thai people but also for Asian people of similar races and under similar environmental conditions.