This research investigates the gaps between theoretical knowledge and the practical implementation of the Pre-Exposure Prophylaxis (PrEP) policy in Brazil, particularly among young people, through the Social Determinants of Health (SDH) approach. To this end, I present the historical trajectory of the formation of the concept of SDH in the 19th and 20th centuries, leading up to its formalization by the World Health Organization in 2005. Based on a qualitative methodology using secondary and primary sources such as documents, databases and interviews, I analyze the socio-political context that shapes health interventions in Latin America, emphasizing the Brazilian experience in the light of the SDH. Subsequently, through two empirical projects on PrEP in Brazil, I demonstrate the challenges faced by young people in accessing and adhering to prophylaxis, two central concepts in the SDH approach. To do this, I use a model by Dahlgren and Whitehead as a lens to understand how the SDH relate to each other. I also highlight the possible contributions of these projects to the dissemination of PrEP in the Unified Health System (SUS), with an emphasis on the role of peer educators. The research reveals that effective solutions for adherence in prophylaxis projects require approaches such as the SDH, which, when it comes to implementation, present a series of challenges to health policy makers and agents.