--- - |2 Abstract In this paper, we reflect on health intervention translations as matters of their implementation practices. Our case is methadone treatment, an intervention promoted globally for treating opioid dependence and preventing HIV among people who inject drugs. Tracing methadone's translations in high‐security prisons in the Kyrgyz Republic, we notice the multiple methadones made possible, what these afford, and the onto‐political effects they make. We work with the idea of the ‘becoming‐methadone‐body’ to trace the making‐up of methadone treatment and its effects as an intra‐action of human and nonhuman substances and bodies. Methadone's embodied effects flow beyond the mere psycho‐activity of substances incorporating individual bodies, to material highs and lows incorporating the governing practices of prisoner society. The methadone‐in‐practice of prisoner society is altogether different to that imagined as being in translation as an intervention of HIV prevention and opioid treatment, and has material agency as a practice of societal governance. Heroin also emerges as an actor in these relations. Our analysis troubles practices of ‘evidence‐based’ intervention and ‘implementation science’ in the health field, by arguing for a move towards ‘evidence‐making’ intervention approaches. Noticing the onto‐politics of health intervention translations invites speculation on how intervening might be done differently. - 'Sociology of Health &Illness, EarlyView. '