What is a standard initial therapy for latent TB infection?

• A. Isoniazid for 6–9 months
• B. Rifampin for 4 months
• C. Pyrazinamide for 6 months
• D. Ethambutol for 9 months

Answer: (A)

Preventing progression from latent TB infection to active disease relies on preventive therapy. The traditional first-line option is isoniazid given daily for about 6–9 months. This regimen has long-standing, well-established evidence showing it reduces the risk of developing active TB, and completion rates are favorable when a prolonged course is used. While shorter options exist, such as rifampin for 4 months, those are generally considered alternatives for specific situations (like INH intolerance or confirmed INH resistance) rather than the standard initial choice. Pyrazinamide or ethambutol are not used as routine initial regimens for latent infection because they lack favorable safety and efficacy profiles for LTBI when used alone or in the common preventive context; they are more relevant to activity-based multidrug regimens for active TB.