 - Third group will receive 100 mgday of Isoniazide on day 1 which is gradually increased to maximum dose 5mgkgday by day 4 and continued. Rifampicin is introduced on day 8 in a dose of 150 mgday which is gradually increased to maximum dose 10mgkgday by day 11 and continued. Pyrazinamide is introduced on day 15 in a dose of 500mgday which is gradually increased to maximum dose 25mgkgday by day 18 and continued. 