Possible Interaction: Rifampin 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.”

“Treatment with dexamethasone, phenobarbital, rifampicin , or 1α,25-dihydroxyvitamin D3 resulted in 5.8-fold, 13.4-fold, 9.8-fold, or 95.0-fold induction of CYP3A4 expression relative to that in the untreated controls, respectively.”

“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.”

“A 2‐wk course of rifampicin orally (600 mg/day) in 8 male subjects resulted in a consistent fall in plasma 25‐hydroxycholecalciferol (25‐OHD) levels of around 70%, accompanied by increased oxidation of antipyrine and 6β‐hydroxycortisol (indicative of hepatic enzyme induction).”

“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.”

“ CC‐I enhanced the Cmax by 35% and AUC by 53% of RIF.”