A frequently recounted episode in the history of early modern medicine concerns the physician Adrian Helvetius’s introduction of ipecacuanha to French medical practice in the late seventeenth century, following his successful cure of Louis XIV’s son of dysentery using this medicinal drug. Yet to this day, the Helvetius story remains riven with contradictions, obscurity and confusion, even down to the nature of the drug involved. This article, challenging histories of “information” as homogeneous and neutral, explores the crafting of Helvetius’s reputation as physician and pharmaceutical entrepreneur through print and correspondence. Rather than seeking to establish a definitive account of ‘what actually happened’, it addresses the ways in which different media shaped and mediated the politics of knowledge surrounding Helvetius and his drug. Considerations of intellectual and commercial property inflected medical knowledge in different ways, producing distinct strategies of publicity. While Helvetius capitalised on courtly connections to promote himself and his drug, rivals eyed the Republic of Letters as an alternate route for establishing natural knowledge-claims. Yet the arch-newsmonger of the Republic of Letters, Gottfried Wilhelm von Leibniz, elected to preserve the connection between Helvetius and ipecacuanha in print. I argue that Leibniz’s actions stemmed from a view of the public domain which downplayed discovery and emphasised the disclosure of medical secrets in the public interest.