[Sequential development of vitamin D metabolites under isoniazid and rifampicin therapy]

A sequential study of 25-hydroxy vitamin D (25-OH-D), 1.25 dihydroxy vitamin D [1.25 (OH)2-D], PTH, alkaline phosphatase and gammaglutamyl transpeptidase (gamma GT) was undertaken in a series of 46 children with asymptomatic tuberculosis treated by isoniazid (INH) alone or associated with rifampin (RMP). These parameters were measured before treatment, 1 month, 3 months after the onset and at the end of treatment (6 months). In order to reduce the influence of the time of the year on the 25-OH-D levels, 22 patients were selected for whom the whole treatment took place between October and May of the following year. In this group, 13 children were treated by INH and RMP, 9 by INH alone. A statistically significant decrease in 25-OH-D levels could be demonstrated after 3 months of treatment in 13 patients under INH and RMP as well as a significant increase in alkaline phosphatase and gamma GT levels. In 9 patients given INH alone, 1.25 (OH)2-D levels decreased after 3 months without significant changes in 25-OH-D, alkaline phosphatase or gamma GT levels. These results emphasize the need for regular biochemical supervision, even if no sign of rickets is observed in these patients.