Which drugs comprise the standard initial four-drug regimen for active tuberculosis?

Which drugs comprise the standard initial four-drug regimen for active tuberculosis?

• A. Rifampin, Isoniazid, Pyrazinamide, Ethambutol (± Streptomycin)
• B. Isoniazid alone
• C. Rifampin only
• D. Pyrazinamide and Ethambutol only

Answer: (A)

Tuberculosis treatment relies on multiple drugs from the start to prevent the bacteria from developing resistance. The standard initial four-drug regimen includes rifampin, isoniazid, pyrazinamide, and ethambutol. Each drug adds a different mechanism, providing broad coverage against both actively growing bacteria and persistent bacilli. Rifampin inhibits RNA synthesis, isoniazid blocks mycolic acid formation in the cell wall, pyrazinamide disrupts membrane energetics at acidic pH, and ethambutol interferes with cell wall synthesis while helping prevent resistance. This combination dramatically reduces the bacterial load quickly and lowers the risk of resistance compared with using a single drug. Streptomycin can be added in some cases when susceptibility is uncertain or in drug-resistant TB, but it is not routinely part of the standard initial four-drug regimen.

Tuberculosis treatment relies on multiple drugs from the start to prevent the bacteria from developing resistance. The standard initial four-drug regimen includes rifampin, isoniazid, pyrazinamide, and ethambutol. Each drug adds a different mechanism, providing broad coverage against both actively growing bacteria and persistent bacilli. Rifampin inhibits RNA synthesis, isoniazid blocks mycolic acid formation in the cell wall, pyrazinamide disrupts membrane energetics at acidic pH, and ethambutol interferes with cell wall synthesis while helping prevent resistance. This combination dramatically reduces the bacterial load quickly and lowers the risk of resistance compared with using a single drug. Streptomycin can be added in some cases when susceptibility is uncertain or in drug-resistant TB, but it is not routinely part of the standard initial four-drug regimen.