Hello there, Atripla itself interferes with fat metabolism and hence may lead to a mild weight gain. Since Oxyelite pro contains fat burning compounds like Rauwolfia and Cirsium oligophyllum they cancel each other out and hence you may not see any net effects. As in your weight loss with oxyelite pro may not be that significant. Regarding safety it is safe to use atripla with oxyelite pro but you may not see the results you want. Also If you are on atripla keep a watch out for supplements containing creatine as then your kidney fucntions may get affected. Hope this helps, Please feel free to address any further queries to me,