Nonprofit efforts to develop ±3,4‐methylenedioxymethamphetamine (MDMA)—better known as the street drug Ecstasy—as a prescription pharmaceutical provide the opportunity to examine recent theorizations of pharmaceuticals as fluid objects transformed in new informational and material environments. Drawing from ethnographic research, this article interrogates MDMA researchers’ own distinction between MDMA and the street drug Ecstasy. While researchers maintain that pure MDMA is distinct from Ecstasy, this article argues that the difference between the two hangs not on a distinction in substance, but on a distinction in safety that must be produced through the trial. This article tracks the production of safety through the inter‐connected work of clinical documents, which manage both which bodies are allowed to absorb the drug and which bodily events count as effects. MDMA’s safety emerges from the careful management of relations through these documentary practices.