Drug interaction between rifampicin and cotrimoxazole in patients with tuberculosis.

1. Patients (n = 15) who were admitted with complications of tuberculosis, were given antitubercular therapy (ATT) with rifampicin (RIF), for a minimum period of 15 d, and cotrimoxazole (CTZ), concurrently, for 5-10 d. 2. The serum RIF levels were measured before the start of CTZ treatment and at the end of its administration. 3. The plasma half-life (t1/2) of RIF increased significantly from 1.92 +/- 0.57 h to 2.31 +/- 0.134 h after CTZ treatment. 4. The mean serum levels of RIF increased significantly at 4 and 6 h after CTZ administration.