The primary anti-TB medicines are Isoniazid (H), Rifampicin(R), Pyrazinamide (Z), Streptomycin (S) and Ethambutol (E). Apart from Streptomycin, the drugs are used in fixed-dose combination (FDC) tablets. Treatment regimens for new cases and retreatment exist for adult patients. Treatment is in two phases: an intensive phase (two or three months) and a continuation phase (four or six months). The initial intensive phase aims to kill the TB bacteria rapidly. The continuation phase of treatment aims to destroy any lingering bacteria that could trigger a relapse. Treatment in the intensive phase is directly observed by a treatment supporter.