American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the first line therapy for a patient diagnosed with active tuberculosis?

1. Rifampin and isoniazid alone

2. Only isoniazid

3. Rifampin, isoniazid, pyrazinamide, and ethambutol

4. Isoniazid and ethambutol

The correct answer is: Rifampin, isoniazid, pyrazinamide, and ethambutol

The first-line therapy for active tuberculosis is a combination of four drugs: rifampin, isoniazid, pyrazinamide, and ethambutol. This regimen is essential as it targets the tuberculosis bacteria effectively while also minimizing the risk of developing drug resistance. Rifampin and isoniazid are potent agents that work together to disrupt the synthesis of the bacterial cell wall and nucleic acids, leading to the death of the Mycobacterium tuberculosis organism. Pyrazinamide enhances the effectiveness of rifampin and isoniazid, especially in acidic environments, which are typically found within the granulomas formed in the lungs affected by tuberculosis. Ethambutol adds a further layer of coverage by inhibiting the synthesis of the bacterial cell wall, specifically interfering with arabinogalactan metabolism. This multi-drug approach is crucial not only for successfully treating the infection but also for reducing the chances of treatment failure and preventing the emergence of resistant strains of tuberculosis. Monotherapy, such as the use of isoniazid alone, is inadequate because it does not provide the necessary coverage against resistant bacteria, and can lead to treatment failure and progress of the disease. In summary, the combined use of rifampin,