RESUMEN
Serum levels of theophylline were determined in 54 asthmatics children aged 3,92 +/- 2,45 years, who were taken oral theophylline at doses of 4,99 +/- 0,45 mg. The serum levels at 0 hours (9,22 +/- 4,90 mcg/ml) and at 2 hours (15,22 +/- 5,5 mcg/ml) showed a great variation, although they were taken similar doses. Two hours after ingestion, 34 patients showed levels between 10-20 mcg/ml in 10 children were less than 10 mcg/ml, and another 10 shown serum levels over 20 mcg/ml without symptoms. There was a good correlation between levels at 0 and 2 hours (p less than 0,002). These data may support the utility of doses employed. It is advisable knowing the individual response to theophylline for managing episodes of asthma in children, that can be made by only one determination 2 hours after ingestion.