Drug interaction between rifampicin, isoniazid and cotrimoxazole in rabbits.

1 The results of cotrimoxazole (CTZ) co-administration (15 mg kg-1 trimethoprim + 40 mg kg-1 sulphamethoxazole) on plasma concentration and various pharmacokinetic parameters of rifampicin (RIF, 24 mg kg-1) and isoniazid (INH, 14 mg kg-1) were studied. 2 In the test group (n = 6), CTZ was administered on the 24th day of antitubercular treatment (ATT) and given for 7 d. 3 At the end of concurrent treatment with CTZ, RIF half-life (t1/2) and plasma concentration were both increased. However, there was no effect on INH half-life and plasma concentration.