Effect of rifampicin on the enterohepatic recycling of estrogen in female tuberculous patients

Abstract

Enterohepatic recycling of estrogen after oral administration of 1 mg non-radioactive estriol was studied in ten women taking rifampicin as one of the antitubercular drugs and in fourteen healthy women selected as control subjects. The extent of enterohepatic recycling of estriol (E(3)) during early follicular phase of menstrual cycle was assessed by monitoring for 48 hours the urinary excretion of its two major metabolites i.e., estriol-16alpha-glucuronide (E(3)-16alpha-G) and estriol-3-glucuronide (E(3)-3-G). Of these metabolites the former is synthesized in liver as well as in the gut where as later is synthesized exclusively in the gut, hence the change in urinary level of H(3)-3-G with respect to E(3)-16alpha-G was considered to reflect the extent of enterohepatic recycling of E(3). The levels of both metabolites in urine were determined by radioimmunoassay. Lower values of variables including E(3)-3-G output, E(3)-3-G output as % of the total (E(3)-16alpha-G + E(3)-3-G) excretion and total E(3) (E(3)-16alpha-G + E(3)-3-G) output as % dose and the diurnal variation in urinary excretion of these metabolites show that the final elimination of E(3) from the body was quicker in these patients as compared with the control subjects, probably due to the reduced extent of enterohepatic recycling of E(3) as a result of long term chemotherapy with rifampicin.