Vitamin K deficiency with erythromycin. Observation of a boy treated with valproate

A nine year old boy had been treated with valproic acid during one and a half years because of a grand mal epilepsy. Under an additional medication with erythromycin succinate syrup this patient developed a deficiency of prothrombin-complex, which was reversible immediately after oral intake of vitamin K. In this case it is assumed that the simultaneous application of both valproic acid and erythromycin succinate seems to suppress the vitamin K producing intestinal tract bacteria, which has not been reported in the literature so far.