Purity of consumer-level methamphetamine samples and methamphetamine-adulteration of other drugs: Los Angeles, 2023-2024

Abstract Background National trends indicate a rise in both methamphetamine-involved deaths and people living with methamphetamine-use disorders. Reports from the Department of Justice and Drug Enforcement Agency indicate methamphetamine seized during criminal investigations is almost uniformly high purity. However, there remains limited information on the purity of methamphetamine at the consumer level. Methods Anonymous participants accessing a community-based drug checking program voluntarily provided samples of illicit drug product and completed brief interviews in Los Angeles County, California from February 2023 to November 2024. Samples underwent laboratory-based qualitative direct analysis in real time mass spectrometry and liquid chromatography mass spectrometry to quantify a panel of twelve substances. Statistical methods were used to determine differences between co-detected substances among samples expected to be methamphetamine and samples where methamphetamine was detected but unexpected. Results Of 201 samples expected to be methamphetamine, 88% (n=177) contained only methamphetamine, with the average freebase purity of 68 of those samples being 58%, ranging from 0.1%-96%. Methamphetamine was also detected in 87 samples of other expected drugs, such as fentanyl, MDMA, and heroin. Conclusion Methamphetamine tested at the consumer-level was found to primarily contain only methamphetamine, despite heterogeneous and highly variable purity. Methamphetamine was also frequently found to be an adulterant in other substances rather than a target of adulteration, which may indicate unwitting exposure among people intending to use other drugs. Given the physiological and psychological effects of chronic methamphetamine use, future research should expand methamphetamine surveillance techniques and investigate how variability in purity may impact health outcomes.