Evaluation of Theophylline Dosing Equation in Korean Infants with Bronchial Asthma

Choi, Deok Cheol; Jung, Young Hye; Youn, Un Ki; Oh, Ji Sub; Park, Yeun Ju; Sands, Charles D; Cha, Hye Ri

Abstract

It has been reported that theophylline clearance is lower in Korean infants than in Americans, suggesting that dose requirements for theophylline in Korean infants will be 1ower than those in Americans. Therefore, we reviwed patients charts retrospectively to formulate the new theophylline dosing equation appropiate to Korean infants. We reviewed patient charts of 111 asthmatic infants who received intravenous aminophy1line and oral theophylline in Wa1lace Memorial Baptist Hospital. We set the therapeutic serum concentration at 5-15microgram/ml in Korean infants based on response rate to theophylline therapy, which is supported by National Institute of Health Expert Panel Recommendations. Doses required to achieve a therapeutic serum concentration increased with age. The mean dose among the infants less than 4 months of age was 578+/-154mg/kg/day and increased to 10.12+/-1.78mg/kg/day after 8 months (p<0.0001). The relationship between age and dosage requirements can be expressed by the least squares determination of the linear regression :Dose (mg/kg/day) = 557 + 0.14 X (age in weeks). The coefficient of correlation for this relationship is 0.67(p<0.0001). Half-lives of elimination among the infants studied correspondingly decreased with age. In conclusion, this study showed that the relationship between age and dosage requirements in Korean infants may be different from those in Americans. Therefore, we strongly suggest that it is required to formulate a new theophylline dosing equation appropriate for Korean infants through well-designed prospective studies.