Effect of Asthmatic Acute Phase on Theophylline Clearance in Japanese Pediatric Patients during Constant Aminophylline Infusion

The changes in theophylline clearance in 115 Japanese pediatric patients (72 males and 43 females) aged from 0.5 to 4 years undergoing a constant rate aminophylline infusion were investigated during the asthmatic acute phase.Plasma theophylline concentration data,which were retrospectively obtained from routine therapeutic drug monitoring,were divided into 2 groups according to the time from initiation of aminophylline infusion (up to 48 hours or more than 60 hours) in order to estimate theophylline clearance.In male patients,the theophylline clearance estimated for more than 60 hours was 27% higher than that for up to 48 hours (p<0.01)for ages 2-<5 years.In female patients,the theophylline clearance estimated for more than 60 hours was 35% higher than that for up to 48 hours (p<0.05)for ages 2-<5 years.Our findings suggested that the theophylline clearance estimated for more than 60 hours from the initiation of a constant aminophylline infusion could not be safely used in setting the next initial dose of aminophylline in the asthmatic acute phase in pediatric patients.