Tuberculosis patients may find that their urine is red during treatment with the drug, and even stool, saliva, tears, sputum and sweat can be red. This is because of the administration of rifampin. Rifampin is an antibiotic with color, and its color-producing gene is a quinone or hydroquinone aromatic nucleus on the chemical structure. Let’s start with a brief look at the absorption, distribution and excretion of rifampicin. After patients take rifampicin, the drug is quickly absorbed into the blood and widely distributed in the liver, bile, kidneys, lungs, cerebrospinal fluid and soft tissues, and has a high concentration. Rifampicin is mainly excreted by the biliary and intestinal tracts, with 60-85% excreted in the feces. About 1/3 of rifampicin is excreted in the urine. A small proportion of rifampicin is excreted by saliva, tears, sputum and sweat. Geng Shujun, Department of Tuberculosis Medicine, Hebei Chest Hospital, Hebei Province, China Rifampin and its metabolites all appear orange-red, so stool, urine, saliva, tears, sputum and sweat also appear red. In addition, rifampicin is a fat-soluble drug, and the fatty substance is added to the compound rifampicin capsule, so its solubility is greatly improved, and it can be rapidly absorbed by the small intestine after taking, and the blood concentration is increased, so the urine is red.