SAN FRANCISCO, CA—The completion rate of a 12-dose, 3-month isoniazid/rifapentine (3HP) regimen in this study (83.7%) is comparable to its completion rate in Study 26 (82.1%), and is significantly higher than the average 55.0% completion rate for the 9-month isoniazid regimen that was reported in Arkansas for the past 5 years, according to results presented at IDWeek 2013.

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Arkansas is one of several sites in the U.S. that is collaborating under CDC guidance, to assess adverse events (AEs) associated with the 3HP regimen to treat latent tuberculosis infection (LTBI). Naveen Patil, MD, MHSA, MA, from the Arkansas Department of Health, Little Rock, AR, and colleagues aimed to characterize and assess the adverse effects of the 12-dose 3HP regimen during the period of July 1, 2012—August 31, 2013.

Directly observed therapy (DOT) is used for a 3-month isoniazid/rifapentine regimen. At each weekly visit, nurses completed a form created by the CDC to capture AE data.

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Since July 2012, a total of 796 cases of LTBI have been reported, a majority of which had a positive IGRA test. Of these, 526 cases were offered 3HP, and 270 received either the isoniazid or rifapentine regimen. A total of 277 patients of the 331 (83.7%) offered 3HP with complete outcome information completed the regimen.

The frequencies of AEs were as follows: flu-like illness 23.6%, gastrointestinal 20.2%, and cutaneous 6.0%. No deaths or hospitalizations were directly associated with 3HP. The 331 cases on 3HP with complete outcome information are similar to the 195 pending cases in terms of median age, gender, and race/ethnicity.

“The frequency of adverse effects in our study, at 31.1% are much higher than what was reported in Study 26,” noted Dr. Patil. The frequencies of AEs as reported in Study 26 were as follows: flu-like illness 2.2%, gastrointestinal 0.2%, and cutaneous 0.6%.  A possible explanation of these results was that this study was specifically designed to assess these AE, whereas Study 26 was not.

Dr. Patil expressed that “the 3HP regimen has potential to impact the goal of tuberculosis elimination but the correlation between flu-like AEs and seasonal influenza needs further study.”