Moxifloxacin, when used as part of a shorter treatment regimen for drug-resistant tuberculosis (DR-TB), appears not to increase the risk for prolonging the QT interval (ie, interval between heart contraction and relaxation — the Q through T waves seen on electrocardiogram). This was among study results recently published in the Journal of Clinical Tuberculosis and other Mycobacterial Diseases.

Moxifloxacin, which is considered to be among the most effective agents against DR-TB that is a component of the shorter DR-TB treatment regimen, has been suspected of  increasing the risk for prolonging the QT interval. To determine the validity of this suspicion, researchers sought to determine whether a correlation existed between the QTc interval (QT interval corrected for heart rate) and levels of moxifloxacin concentration in patients with rifampicin-resistant (RR)-TB in short treatment regimens.

In the current observational study, researchers assessed 2 groups of patients with RR-TB on shorter treatment regimens containing moxifloxacin who received body weight-adjusted dosing: (1) 29 adult patients in the intensive phase of treatment (median age, 37 years; 13 female; QTc baseline 417.28±31.2); and (2) 16 patients in the continuation phase of treatment (median age 44 years; 9 female; QTc baseline 455.94±16.6).


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the investigators found that the mean of the QTc interval 2 hours following the 48th-hour dose was 444.38 ms in the intensive phase cohort and 467.94 ms in the continuation phase cohort (P =.026), and that the mean moxifloxacin concentration in the intensive phase was 4.3 µg/mL vs 4.61 µg/mL in the continuation phase  (P =.686). Further analysis showed that there was no correlation with moxifloxacin concentration and QTc interval in either the intensive phase (P =.576) or the continuation phase (P =.691).

The mean of the QTc interval in the intensive phase and the continuation phase at 1 hour prior to the 72nd-hour dose also revealed no significant difference (P =.610 and P =.325, respectively), and there was likewise no correlation between moxifloxacin concentration and QTc interval in the intensive phase (P =.531) or the continuation phase (P =.209).

Researchers concluded that, “Moxifloxacin concentration did not correlate with QTc interval, which indicates the safe use of moxifloxacin on QTc interval.” However, the investigators urged clinicians to carefully monitor QTc interval and other properties that might add to QTc prolongation risk in DR-TB patients receiving shorter treatment options.

Reference

Kusmiati T, Mertaniasih NM, Putranto JNE, et al. Moxifloxacin concentration correlate with QTc interval in rifampicin-resistant tuberculosis patients on shorter treatment regimens. J Clin Tuberc Other Mycobact Dis.Published online June 6, 2022. doi:10.1016/j.jctube.2022.100320