For latent TB infection prophylaxis, which drug is commonly used in monotherapy?

For latent TB infection prophylaxis, which drug is commonly used in monotherapy?

• A. Isoniazid
• B. Rifampin
• C. Pyrazinamide
• D. Ethambutol

Answer: (A)

In latent TB infection, the goal of prophylaxis is to eradicate dormant mycobacteria and prevent reactivation, using a single drug when possible. Isoniazid is the classic choice for monotherapy because it has strong, well-established efficacy in this setting. It works after being activated by the bacterial enzyme KatG to block mycolic acid synthesis, a vital component of the mycobacterial cell wall. Because the bacteria are slow-growing and mostly dormant in latent infection, a longer course of therapy is needed; typically daily isoniazid for about 6 to 9 months is prescribed, with 9 months offering slightly better protection in many guidelines. Rifampin can be used as an alternative monotherapy, particularly for people who cannot take isoniazid or when INH resistance is a concern, but it is generally less commonly used as the first-line option for latent infection. The other drugs listed are not used as single-agent regimens for latent TB prophylaxis because they lack the same demonstrated efficacy in this context or are primarily reserved for active TB treatment regimens rather than latent infection. So, isoniazid monotherapy remains the standard approach for latent TB infection prophylaxis due to its proven effectiveness and long-standing use in this role.

In latent TB infection, the goal of prophylaxis is to eradicate dormant mycobacteria and prevent reactivation, using a single drug when possible. Isoniazid is the classic choice for monotherapy because it has strong, well-established efficacy in this setting. It works after being activated by the bacterial enzyme KatG to block mycolic acid synthesis, a vital component of the mycobacterial cell wall. Because the bacteria are slow-growing and mostly dormant in latent infection, a longer course of therapy is needed; typically daily isoniazid for about 6 to 9 months is prescribed, with 9 months offering slightly better protection in many guidelines.

Rifampin can be used as an alternative monotherapy, particularly for people who cannot take isoniazid or when INH resistance is a concern, but it is generally less commonly used as the first-line option for latent infection. The other drugs listed are not used as single-agent regimens for latent TB prophylaxis because they lack the same demonstrated efficacy in this context or are primarily reserved for active TB treatment regimens rather than latent infection.

So, isoniazid monotherapy remains the standard approach for latent TB infection prophylaxis due to its proven effectiveness and long-standing use in this role.