[Measurement of blood theophylline levels in the child: will this affect methods of prescription? (author's transl)].

Twelve children aged between 2 and 13 years received an oral dose of 5 mg/kg of pure theophylline, and 28 children aged between 2 and 15 years were given 10 mg/kg/day of the same drug in 3 or 4 divided doses for 3 days. In the first group blood theophylline levels were higher than 10 microgram/ml, after 1 or 3 hours, in only 3 children, two of whom were receiving erythromycin at the same time. Six hours and 12 hours later, none of the serum levels were higher than 10 microgram/ml. In the second group, estimations were performed on the 4th day. At 8 a.m., when the last dose had been given 12 hours previously, blood theophylline levels were all less than 10 microgram/ml (mean: 4.03 +/- 0,88 microgram/ml). Two hours and four hours after the usual morning dose, serum levels of greater than 10 microgram/ml were found in respectively 35 and 25% of the children only. Since the bronchodilator effect of theophylline is optimal for serum levels of greater than 10 microgram/ml, the dose currently recommended in France (10 mg/kg/day) would thus appear to be insufficient in most instances. However, increase in individual doses must be guided by serum estimations, which make it possible to avoid complications related to overdosage.