What is the continuation phase of TB treatment?

• A. 3 drugs: isoniazid, rifampin, ethambutol for 18 weeks
• B. 2 drugs: isoniazid and rifampin for 6 months
• C. 2 drugs: isoniazid and rifampin for 18 weeks
• D. 4 drugs for 9 months

Answer: (C)

The continuation phase is the period after the initial intensive phase where the goal is to finish eradicating lingering organisms with a simpler regimen. After the first 8 weeks of four-drug therapy, you switch to two drugs—isoniazid and rifampin—for about 18 weeks to complete a six-month course of treatment. Using only these two drugs during this phase provides the necessary sterilizing activity to prevent relapse while minimizing drug exposure and toxicity from the other agents used earlier. The other choices don’t fit this pattern: a three-drug continuation plan isn’t typical, six months of just two drugs isn’t the standard continuation duration, and four drugs for nine months reflects a different, longer initial or special-case regimen rather than the standard continuation approach.