In 1944, Waksman develops Streptomycin, the first antibiotic. PAS appears in 1946, INH follows in 1952 and Rifampicin in 1965. Resistance to medical drugs leads to criteria regarding combination and length of medical R/. New insights gained from R/ studies allow modifications of R/ and adjustment of criteria.

At present, TB in industrialized countries is treated with a combination of 4 antibiotics: INH, (isoniazid) RMP (rifampicin), PZA(pyrazinamide), EMB(ethambutol) in the induction phase (2 – 3 mo.), followed by 2 antibiotics: INH, RMP in the consolidation phase (4 mo). in subjects with a normal immune status and normal antibiotic sensitivity studies.

R/ is started empirically with INH, RMP, PZA and EMB.

Drug sensitivity studies become available usually in the 3^rd month of treatment, when R/ continuation / adjustment follows.