Volumetric dilution nasal spray as a harm reduction strategy for intranasal psychoactive substance use: a practical framework and rationale

Abstract Background Intranasal insufflation of psychoactive substances, including cocaine, MDMA, and ketamine, is associated with a well-documented spectrum of nasal and sinonasal complications. These result from at least three distinct but interacting mechanisms: mechanical trauma from particulate matter, vasoconstriction-induced mucosal ischaemia (primarily relevant for cocaine), and chemical irritation from adulterants. Harm reduction (HR) programmes have traditionally focused on hygiene, shared equipment, and product testing, but the form of the substance itself, solid powder versus aqueous solution, has received little formal attention. Main body Volumetric dilution nasal spray (VDNS) is an approach in which the substance is dissolved in sterile saline and delivered via a calibrated spray device. This method eliminates mechanical mucosal trauma from powder particles, delivers the substance in a hydrated vehicle compatible with mucosal physiology, and converts an uncontrolled line-based dosing practice into a quantifiable per-spray unit. Drawing on pharmaceutical nasal delivery science, existing HR resources from community organisations, and field feedback from harm reduction professionals, this article describes the rationale, practical implementation, limitations, and field integration of this approach for cocaine, MDMA, and ketamine. The method is grounded in the pharmacokinetics of intranasal absorption, the known pathophysiology of snorting-related nasal damage, and the principles of non-normative harm reduction. Conclusion VDNS represents a low-barrier, low-cost HR intervention that is coherent with existing national and international HR frameworks. Formal evaluation of its acceptability and impact on nasal morbidity is needed. Pending such data, its dissemination by HR professionals in community settings is supported by biological plausibility and field practice.