What is a primary reason for using a multi-drug TB regimen?

• A. To shorten therapy time
• B. To prevent resistance
• C. To simplify dosing
• D. To reduce liver toxicity

Answer: (B)

Using multiple drugs in TB treatment is essential to stop the bacteria from developing resistance. TB bacteria can mutate and survive a single drug, so if you treated with just one medication, resistant mutants could persist and multiply, leading to treatment failure and spread of resistant TB. By combining several drugs with different targets and mechanisms, the chance that a bacterium carries resistance to all of them is extremely small, so the regimen is far more effective at killing the organisms and preventing the emergence of drug-resistant strains. This protective effect against resistance is the primary reason for a multi-drug approach, while shortening therapy time or reducing liver toxicity are important considerations but not the main driver.