Antiretroviral dose adjustment is rarely needed for obese people with HIV, modeling study suggests

Except for a few specific situations, antiretroviral (ARV) drug doses do not need to be adjusted for people who are obese, even though drug exposure and trough concentrations are generally lower in those who are obese compared to non-obese people living with HIV (PLWH), reports a modeling study in Switzerland.

About This Study

“Antiretroviral drug exposure and response in obese and morbidly obese people with HIV: a study combining modelling and Swiss HIV Cohort data“ was published online on Aug. 21, 2023, in Clinical Infectious Diseases. The lead author is Mattia Berton, M.S., of the Departments of Medicine and Clinical Research and the Division of Infectious Diseases and Hospital Epidemiology at University Hospital Basel, Switzerland.

Key Research Findings

Since few obese PLWH are included in clinical trials, the current study used virtual adults in virtual trials to model ARV response among people with body mass indices (BMIs) of 18.5-60 kg/m². The model input was therapeutic drug monitoring data from the Swiss HIV Cohort Study (SHCS). Obesity was defined as a BMI ≥ 30 kg/m².

The model predicted lower ARV exposure in obese PLWH for all ARVs, but the degree of reduction differed by drug. Etravirine exposure dropped the most and doravirine exposure the least.

Drug trough concentrations were less affected but most still dropped with increased body mass. In the highest BMI group, dolutegravir troughs decreased by 34% in obese compared to non-obese people. In PLWH with BMI >40 kg/m² (morbidly obese), trough concentrations of etravirine and rilpivirine fell below the clinical threshold. Among that group, tenofovir disoproxil fumarate (TDF) trough levels dropped by up to 30%.

However, these pharmacokinetic data did not translate into impaired virologic response–a result also borne out by observational data from the SHCS, where viral suppression rates did not differ by obesity status.

Discussion Highlights and Implications for Practice

Study authors recommended therapeutic drug monitoring for obese PLWH who take etravirine or rilpivirine to ensure sufficient drug coverage. They advised caution when prescribing TDF post-exposure prophylaxis to morbidly obese patients. Except for these scenarios, drug doses do not need to be adjusted based on BMI, they concluded.

By Barbara Jungwirth