Ethambutol exposure-outcome link found regimen-dependent in TB trial

A population pharmacokinetic/pharmacodynamic analysis using data from Study 31/AIDS Clinical Trials Group A5349, involving 1493 participants with 3077 plasma samples, found that diabetes, higher creatinine clearance, and higher weight were linked to increased ethambutol clearance. The study reported that higher ethambutol exposure was modestly associated with more grade 3 or higher adverse events and with reduced risk of unfavorable TB outcomes, with a higher exposure target required for cure in the 4-month rifapentine regimen (25.6 µg·h/mL) than the 6-month control regimen (8.9 µg·h/mL). Simulations in the study suggested that reducing doses for higher weight bands could lower toxicity risk while maintaining efficacy in the control regimen, but might not achieve target exposure in the rifapentine regimen.

Most relevant for: Patients being treated for tuberculosis with ethambutol-containing regimens, including those with diabetes, altered renal function, or higher body weight, and those receiving 4-month rifapentine-based therapy.

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