Interaction between rifampin and levothyroxine

Rifampin is a potent inducer of hepatic enzymes and is well documented to c ause many clinically significant drug interactions. Studies in normal volun teers have shown its ability to decrease circulating levels of thyroid horm one, while having no effect on thyroid-stimulating hormone (TSH), Reports o f rifampin's effects an patients on hormone replacement in the clinical set ting are of interest since we believe only one such case has been described , We report the case of a man, stable on levothyroxine, who exhibited signi ficantly elevated TSH levels during therapy with rifampin, Thyroid-stimulat ing hormone levels returned to baseline 9 days after discontinuance of rifa mpin.