Which drug in a tuberculosis treatment regimen is associated with the risk of QT interval prolongation?

Moxifloxacin is the drug associated with the risk of QT interval prolongation within a tuberculosis treatment regimen. This fluoroquinolone antibiotic can affect cardiac repolarization, leading to an increased duration of the QT interval on an electrocardiogram. The prolongation of the QT interval can potentially lead to serious arrhythmias, such as Torsades de Pointes, especially in patients who have other risk factors for cardiac issues or are using other medications that also affect the heart's electrical activity.

While the other drugs listed—pyrazinamide, ethionamide, and streptomycin—are important in the treatment of tuberculosis, they do not carry the same risk for causing significant QT interval prolongation. Thus, recognizing moxifloxacin's association with cardiac effects is crucial for patient monitoring and safety during TB therapy.