Why are multiple antitubercular medications prescribed for TB treatment?

• A. To shorten therapy duration
• B. To prevent resistance
• C. To reduce adverse effects
• D. To increase potency

Answer: (B)

TB bacteria can rapidly develop resistance to a single drug. If only one drug is used, any bacteria with a spontaneous mutation that makes it resistant will survive and multiply, leading to treatment failure and potential multidrug resistance. Using multiple drugs with different mechanisms targets the bacteria in several ways at once, so a bacterium would need multiple simultaneous mutations to withstand the whole regimen. That makes resistance far less likely and helps ensure all bacterial populations—both actively dividing and dormant—are eradicated. While multi-drug therapy can improve overall effectiveness and coverage, its main purpose is to prevent the emergence of drug resistance. Shortening therapy isn’t the primary goal, and increased potency or fewer adverse effects aren’t the core reason for using several drugs.