In mid-February 2025, two Forensic Toxicologists from Axis, Stuart Kurtz and Laureen Marinetti, attended the American Academy of Forensic Sciences annual meeting. While there, Stuart presented Axis’s data on nitazenes and Laureen presented Axis’s data on drug screening in vitreous fluid. For additional information please use this link to access previous Axis blog posts regarding nitazenes: https://axisfortox.com/?s=nitazene&post_type=post
As a refresher, nitazenes emerged after the scheduling of fentanyl analogs. This has largely lead to a decrease in new fentanyl analogs found in drug supplies but the rise in other opioids to fill their place. Isotonitazene was the first of these to emerge in 2019 with metonitazene emerging soon after. These are two of the original compounds described in drug patents from their initial clinical investigation. No nitazene compounds were ever approved for human or veterinary use. Nitazene compounds are structurally distinct from fentanyl analogs and morphine-based opioids such as morphine, hydrocodone, and oxycodone. This means that they will not cross-react in techniques that are immunoassay based. N-Pyrrolidino derivatives have emerged since 2023 which were not a part of the originally described compounds in the drug patents. A list of nitazene analogs that Axis can test for can be found in the Comprehensive Panel Specification Sheet here: https://axisfortox.com/test_catalog/comprehensive-drug-panel/
Graph by Stuart Kurtz
Above is a figure from Stuart’s poster that shows the trend of nitazenes by year. In 2024, metonitazene, N-pyrrolidino protonitazene, and N-pyrrolidino metonitazene are the top three by detections. Often times, two or three of these compounds will be detected together. Stuart will be expanding this data set for a presentation at the Midwest Association of Toxicology and Therapeutic Drug Monitoring in April 2025.
Vitreous fluid is located in the eye between the retina and the lens. It is made up of mostly water with trace amounts of inorganic salts, ascorbic and hyaluronic acids. Laureen’s presentation looked at the utility of screening for drugs using vitreous fluid and how this data compared to the same drug screening in blood. The data was from over 120 cases tested by Axis in the normal course of business wherein both blood and vitreous fluid were screened. The table below shows the drug class, the number of drug detections where the drug confirmed in blood in that drug class, and the percentage of time that the drug also confirmed in the vitreous fluid from the same case.
Chart by Laureen Marinetti, PhD
As shown in this table, all drugs did not confirm the same in each class. Drug entry into the vitreous fluid is dependent upon several factors; drug potency, time of death in relation to drug consumption, the chemical and pharmacological properties of the drug, drug volume of distribution, protein binding of the drug, and the drugs ability to cross the blood retinal barrier (BRB). Drugs may diffuse passively or be actively transported across the BRB. Although there are some advantages to testing vitreous fluid, for example it is isolated from blood and other tissues, it is less susceptible to postmortem redistribution and putrefactive changes, vitreous fluid is not a good specimen for general drug screening. Vitreous fluid is a great matrix for testing for electrolytes, glucose, urea nitrogen, creatinine and volatiles.
For more details on both the nitazenes poster and the vitreous fluid presentation, please reach out to us at 317-759-4869 option 3 or [email protected].