The rise of nitrous oxide in toxicological casework: no laughing matter.

Nitrous oxide (N2O), the colorless, odorless gas known as "laughing gas," has gained recent attention for its misuse as a recreational drug. As an anesthetic, N2O produces sedation, euphoric, and possible hallucinogenic effects. Adverse effects may include disorientation, psychomotor retardation, hypoxia, and asphyxia. N2O misuse has grown due to its ease of availability, rapid onset of effects, and increased social media attention, leading to anticipated increases in forensic testing needs. Due to its short half-life and volatility, analytical detection can be challenging. From January 2022 through September 2025, over 1700 cases were analyzed for N2O using headspace-gas chromatography-mass spectrometry (HS-GC-MS) over a calibration range of 1.8-180 mcg/mL. Total test requests and percent positivity increased during this timeframe for both driving (DUID) and postmortem (PM)/clinical casework. Blood, brain, liver, lung, and urine yielded positive detections. Attempts at repeat testing indicate significant losses in analyte concentrations. Consideration of pre-analytical and analytical factors is critical for suspected inhalant casework. Overwhelmingly, both DUID and PM casework noted N2O canisters present at the scene. Common driver behaviors included disorientation, slow reaction times, struggling with speech, inability to follow directions, and difficulty maintaining balance. DUID blood draws should be collected as close as possible to the suspected incident. Further review of case histories and testing practices generated handling recommendations for suspected inhalant case samples: fill containers to limit headspace; glass containers and tight-fitted closures are preferred; avoid transferring volume to alternate containers; limit container ingresses; and avoid repeat testing within the same container. Multiple matrices/containers should be collected and preserved, whenever possible, with inhalant testing prioritized over other drugs and/or alcohol. Laboratories should also consider qualitative reporting and/or testing as a one-time analysis. By employing these best practices, an inhalant gas may be better collected and preserved, increasing the chances of detection.