Effect of gender on theophylline clearance in the asthmatic acute phase in Japanese pediatric patients.

The effect of gender on theophylline clearance was investigated retrospectively in 96 Japanese pediatric patients (63 males and 33 females) ranging in age from 0.5 to 8 years and in weight from 6.3 to 36.8 kg. All patients received intravenous constant-rate infusion of aminophylline in the asthmatic acute phase. The theophylline clearances in males and females were 56.2+/-15.4 and 50.1+/-14.2 ml/h/kg for ages 0.5-<2 years, 58.7+/-18.8 and 48.3+/-6.5 ml/h/kg for ages 2-<4 years, and 65.7+/-12.0 and 52.1+/-16.8 ml/h/kg for ages 4-<9 years, respectively. At ages from 2 to 8 years, the theophylline clearance was 20% higher in males than in females (p<0.05). Our findings suggested that the initial dosage of theophylline should be adjusted according to the gender of pediatric patients and particularly in the case of infants.