All TB treatment regimens consist of two different phases.

• During initial or intensive phase, a patient classified as a new case of TB will take 4 drugs: HREZ for pan-sensitive TB. The initial phase is used to rapidly kill M. tuberculosis bacilli, stop infectiousness, and prevent selection of resistance.


• During the following 4–6 months, called the continuation phase, the patient classified as a new case will take two drugs, either daily or intermittently (three times per week). The regimen recommended for each patient depends on the diagnostic category for that patient. This phase serves to kill the remaining M. tuberculosis bacilli and sterilizes the lesion.