Why are second-line drugs used in MDR-TB regimens?

• A. To overcome resistance and prevent relapse, requiring prolonged treatment
• B. To reduce cost
• C. To shorten therapy
• D. To avoid all side effects

Answer: (A)

In MDR-TB the bacteria are resistant to the standard first-line drugs, so treatment must rely on medicines with different mechanisms that can still kill the resistant bacilli. These second-line drugs are used to overcome that resistance and to prevent relapse, because they help kill bacteria that the initial regimen cannot. They tend to be less potent and come with more side effects, which is why they’re given in combination and for a much longer period to ensure a durable cure and to minimize the chance of the bacteria developing further resistance. The focus is not on cutting costs, shortening therapy, or avoiding side effects altogether—those drugs are more expensive, longer, and toxic, but using them properly is what makes cure possible in resistant TB.