Possible Interaction: Isoniazid and Vitamin D

“In vitro studies and studies on human volunteers showed that two of the first-line anti-tuberculosis drugs, isoniazid and rifampicin, reduce 25-hydroxy vitamin D (25[OH]D) concentrations.”

“Antituberculous chemotherapy agents, particularly rif‐ampicin and isoniazid , affect vitamin D metabolism and can create biochemical evidence of vitamin D deficiency.”

“Rifampicin, 600 mg, and isoniazid , 300 mg daily for 14 days, reduced circulating levels of 25‐hydroxy vitamin D (25‐OHD) and 1α, 25‐dihydroxy vitamin D (1,25(OH)2D) by 34% (P < 0.01) and 23% (P < 0.05) in eight healthy subjects.”

“Collectively, our data firstly showed that RIF and co-treatment of RIF and INH can both enhance 25-hydroxylation and 24-hydroxylation of vitamin D , providing novel evidence for the involvement of anti-TB drugs in the metabolism of vitamin D.”

“Because previous studies indicated that cimetidine (CIMET) and isoniazid (ISON) may inhibit vitamin D metabolism in both rats and humans, experiments were conducted to evaluate the influence of these drugs on growth and bone development in male broiler chicks.”

“Both cimetidine and isoniazid inhibited vitamin D 25-hydroxylase activity in vitro.”

“ Isoniazid also inhibits hepatic mixed function oxidase activity and has been reported to depress circulatory levels of hydroxylated vitamin D metabolites.”