Rifampicin is easily absorbed from the gastrointestinal (GI) tract; its ester functional group is quickly hydrolyzed in bile, and it is catalyzed by a high pH and substrate-specific esterases. After about 6 hours, almost all of the drug is deacetylated. Even in this deacetylated form, rifampicin is still a potent antibiotic; however, it can no longer be reabsorbed by the intestines and is eliminated from the body. Only about 7% of the administered drug is excreted unchanged in urine, though urinary elimination accounts for only about 30% of the drug excretion. About 60% to 65% is excreted through feces.