Folate deficiency associated with drug therapy for tuberculosis.

N ASSOCIATION BETWEEN megaloblastic anemia and therapy for tuberculosis has been described previously in five instances.1-3 In three patients megaloblastic erythropoiesis was associated with sideroblastic changes in the bone marrow,1’2 and in two the megaloblastic anemia was attributed .o deficiency of vitamin B12 resulting from malabsorption of this vitamin induced by therapy with para-amiriosalicylic acid.3 Direct determination of serum vitamin concentrations was performed in only one of these five patients. The serum folate concentration was subnormal in this subject, who had a sideroblastic anemia.2 We have recently had the opportunity to study two individuals who developed a megaloblastic anemia during therapy for pulmonary tuberculosis. Folate deficiency was demonstrated to be responsible for the megaloblastic erythropoiesis in 1)0th. This report presents observations made on these two patients, the results of assays for serum folate and vitamin B12 concentrations which have been performed in 120 other patients with pulmonary tuberculosis, and the results of studies concerned with the in vitro effect of antituberculosis drugs on the microbiologic assay systems used to determine folate and vitamin B12 concentrations.