The continuation phase of standard TB therapy includes which combination?

• A. Rifampin and Isoniazid
• B. Pyrazinamide and Ethambutol
• C. Rifampin and Pyrazinamide
• D. Isoniazid and Ethambutol

Answer: (A)

In the continuation phase of standard TB therapy, the regimen relies on two drugs with sustained sterilizing activity to finish off residual bacteria after the initial intensive phase. After the two-month initial phase using four drugs, Pyrazinamide and Ethambutol are stopped, while Rifampin and Isoniazid are continued for about four more months. The reason is that Pyrazinamide and Ethambutol provide rapid kill and resistance prevention benefits mainly during the early phase; once the bacilli have been substantially reduced, the backbone drugs—Rifampin and Isoniazid—maintain sterilizing activity to prevent relapse. So, the continuation phase consists of Rifampin and Isoniazid.