Which four medications are traditionally used together for initial therapy of active tuberculosis?

• A. INH, Rifampin, Pyrazinamide, Streptomycin
• B. Isoniazid, Rifampin, Ethambutol, Streptomycin
• C. INH, Rifampin, Pyrazinamide, Ethambutol
• D. Ethambutol, Rifampin, Pyrazinamide, Streptomycin

Answer: (C)

Initial therapy for active tuberculosis uses four first-line drugs together to prevent resistance and maximize bacterial kill during the early, intensive phase. The standard four-drug regimen is isoniazid, rifampin, pyrazinamide, and ethambutol. This combination, often referred to as RIPE, targets the bacteria with different mechanisms: isoniazid and rifampin as potent sterilizing agents, pyrazinamide active in the acidic environment of caseating lesions to shorten duration, and ethambutol adding another mechanism to help prevent resistance to the core drugs. Streptomycin has been used in the past and may still be used in certain situations, but it is not part of the typical initial four-drug regimen today due to toxicity and the preference for the RIPE combination.