Gastro-intestinal absorption of isoniazid and rifampicin in patients with intestinal tuberculosis

The gastro-intestinal absorption of isoniazid and rifampicin was studied in 12 patients with intestinal tuberculosis (10 slow and 2 rapid acetylators of isoniazid) and compared with that in 18 patients with pulmonary tuberculosis (8 slow and 10 rapid acetylators). Exposure (area under the time-concentration curve), calculated on the basis of serum concentrations of the two drugs at 1, 2, 3, 6 and 8 hours, and the proportion of dose of isoniazid excreted in urine collected over the period (0-8½) hours as isoniccotinyl compounds after drug administration were similar in the 2 groups suggesting no impairment of gastro-intestinal absorption of the 2 drugs in patients with intestinal tuberculosis. It was also observed that there was no delay in the absorption of the 2 drugs in patients with intestinal tuberculosis as compared to that in patients with pulmonary tuberculosis. The absorption of D-xylose, used to assess the absorptive capacity of the proximal small intestine, was also similar and normal in both groups of patients