Most young men participating in a pre-exposure prophylaxis (PrEP) demonstration project saw a small but significant amount of bone loss after starting Truvada, researchers reported at the 15th European AIDS Conference last week in Barcelona. Men who had the most highly protective levels of tenofovir in their blood, consistent with at least four doses per week, saw the largest decreases in bone density.
"Although the BMD losses were generally modest [in this study], their occurrence before attainment of peak bone mass in young men who already have low bone mass may increase their risk of fragility in adulthood," the researchers said.
Tenofovir -- one of the two drugs in the Truvada combination pill -- was approved in 2001 and is one of the most widely used antiretrovirals for HIV treatment. Tenofovir is generally safe and well-tolerated.
Bone loss has been previously observed among HIV-positive adults who include tenofovir in their antiretroviral regimen, among infants whose mothers took tenofovir during pregnancy, and among HIV-negative men and transgender women taking tenofovir as part of PrEP. But this study is unique because it investigated tenofovir-related bone loss over time in HIV-negative adolescents and young adults -- the age at which most people reach peak bone density.
Kathleen Mulligan, M.D., from UCSF and her team looked at bone density changes among participants in ATN 110, a demonstration project investigating the safety and feasibility of PrEP for young gay men. Results from the main study were presented this summer at the International AIDS Society Conference in Vancouver.
Bone mass generally peaks during early adulthood, typically around age 20, after which it begins to gradually decline, Mulligan explained. Peak bone mass is an important predictor of bone fracture risk later in life.
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