A patient's weight made no significant difference in his or her response to antiretroviral therapy containing efavirenz (Sustiva, Stocrin), according to an analysis of the association between weight and time to viral suppression/subsequent viral rebound among European HIV patients. The standard 600-mg dose of efavirenz is appropriate for patients with a wide range of weights, the study authors concluded.
A total of 19,968 patients from the Collaboration of Observational HIV Epidemiological Research Europe (COHERE) study were divided into six groups: group 1 (< 55 kg, 9.1% of study population) was considered underweight, group 2 (between 55 kg and 80 kg, 68.3%) was deemed normal weight, groups 3 through 5 (80 kg to 95 kg in 5-kg increments; 9.1%, 5.8% and 3.5%, respectively) were classified as overweight. Group 6 was composed of people weighing 95 kg or more and comprised 4.3% of the study participants. Out of all the patients, 22.5% were women, the majority of whom (63.3%) fell into the underweight category.
Medication response was measured as the time between the start of antiretroviral therapy and the first undetectable viral load (≤ 50 copies/mL), as well as the time to viral load rebound (two consecutive viral loads > 50 copies/mL) after initial virological suppression. Overall, 81.1% of patients were virologically suppressed at some point; 34.1% of whom subsequently saw their viral load rebound.
No statistical difference in these measurements was observed between people of normal weight and overweight patients. However, those in the underweight group were less likely to have an undetectable viral load (P = .004) and were significantly more likely to experience a virological rebound (P = .0001).
The study authors noted that group 1 included more patients who had acquired HIV through intravenous drug use and more people who had AIDS prior to starting efavirenz. They theorized that the longer time to viral suppression experienced by this group might be explained by poorer medication adherence, later entry into care and a more advanced disease state.
However, the authors cautioned that few severely obese (> 120 kg) patients were included in the study. They recommended that, "response to EFV [efavirenz] should be monitored carefully in severely obese individuals." Obesity rates in Europe range from 7.6% to 24.7% of the population, according to Eurostat, the statistics arm of the European Union. By contrast, 34.9% of the U.S. population is considered obese, according to the U.S. Centers for Disease Control and Prevention.