Relation between theophylline and circulating vitamin levels in children with asthma.

We investigated the effect of theophylline administration on circulating vitamin levels in children with asthma. Twenty-three asthmatic children, ranging in age from 7 to 15 with a mean of 10.8 years and including 16 patients who were treated with slow-release theophylline and 7 patients not receiving any type of theophylline preparation, were enrolled in this study. They all were inpatients who had been hospitalized for the control of asthma. Steady-state serum theophylline and vitamin A, B1, B2, B6, B12 and C levels were evaluated in these patients. Circulating vitamin B1 and B6 levels were depressed in asthmatic children treated with theophylline compared to those not receiving the agent (38.4 +/- 1.6 (mean +/- SEM) vs. 46.4 +/- 3.5 ng/ml and 7.1 +/- 0.5 vs. 11.8 +/- 2.1 ng/ml, respectively, p < 0.05). A significant negative correlation between theophylline and circulating levels of vitamin B6 was demonstrated in the subjects of this study (rs = -0.657, p < 0.001). In contrast, no relationship was noted between theophylline and circulating vitamin B1 levels. Theophylline did not affect circulating vitamin A, B2, B12 or C levels. We conclude that theophylline induces depression of circulating vitamin B1 and B6 levels in asthmatic children, although a dose-dependent interaction between theophylline and vitamin B1 would be unlikely.