Millions of people suffering pain are faced with barriers that prevent them from alleviating unbearable symptoms. This situation is of humanitarian concern and as such raises several key questions: What causes this situation? To what extent and in which ways does the international drug control system contribute to this problem? What is the role of transnational advocacy networks in this process? In answering these questions this study analyzes tensions created by the intersection between the international drug control and human rights regimes. It is focused on the behavior of States that, in the attempt to comply with drug control obligations, undermine the protection of the right to health in the area of access to opioids for pain treatment. To discuss this broad tension in a comprehensive manner, this thesis identifies three relevant levels: Tensions between (1) national sovereignty and States’ international commitments; (2) systematic institutional tensions between the World Health Organizations and the International Narcotics Control Board, and (3) tensions between adequate access to medicines and efforts to eliminate illicit markets. Based on field work interviews, this thesis examines problems faced by patients and practitioners at the national level to trace the reasons for the lack of adequate access to analgesic opioids in Brazil, which is the object of a case study. The analysis covers the period between 2009 - when The Political Declaration and Plan of Action on International Cooperation towards an Integrated and Balanced Strategy to Counter the World Drug Problem was adopted at the Commission on Narcotic Drugs - and 2019, the target date to review achievements of the previous ten years.