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

Introduction The United States (US) has seen a rise in methamphetamine use disorders and methamphetamine-involved deaths. The US Department of Justice and Drug Enforcement Agency reports that seized wholesale methamphetamine is almost uniformly high purity. However, there is limited information on the concentration of methamphetamine at the consumer level. We leverage data from a community-based drug checking program in Los Angeles to investigate (1) the makeup of the retail illicit methamphetamine market and (2) the extent to which methamphetamine plays a role as an adulterant in other drugs. Methods Anonymous participants accessing a community-based drug checking program voluntarily provided samples of illicit drug products and completed brief interviews at four sites in Los Angeles County, California, from February 2023 to January 2026. Samples underwent laboratory-based qualitative testing via direct analysis in real-time mass spectrometry (DART-MS) and quantitative liquid-chromatography mass spectrometry (LC/MS). We quantitated the presence and concentration of methamphetamine as well as all other identified substances among 1) samples expected only to be methamphetamine and 2) samples expected to be another substance (e.g., fentanyl, heroin) where methamphetamine was found as an adulterant/contaminant. Results Of N=2193 total samples, n=652 (29.7%) were methamphetamine-positive on DART-MS. Among methamphetamine-positive samples, the drug was an expected component in two thirds of samples and unexpected in one third. In samples expected to contain methamphetamine, the mean purity was 78.2% (SD 24.0%; range <1% to ≈100%). As an unexpected component, the mean methamphetamine purity was 17.8% (SD 32.3%), and was mostly commonly found in samples expected to be fentanyl, heroin, MDMA, other amphetamines (e.g., counterfeit Adderall), and 2C-B. Conclusions Consumers in Los Angeles seeking methamphetamine appear to frequently obtain high-purity samples that are rarely adulterated with other substances, although we observed a wide variation in concentration between samples. In contrast, drugs purchased without the expectation of containing methamphetamine had substantively high prevalence of methamphetamine adulteration/contamination. Both intentional and unwitting consumers may be vulnerable to the health risks of potent and variable methamphetamine, including psychiatric, cardiovascular, and other illnesses. Future research should expand methamphetamine surveillance techniques and investigate how variability in illicit markets may impact health outcomes. Highlights Samples expected to contain methamphetamine had a mean purity of 72% (SD 24%). For 90% of samples expected to be meth, no other active compounds were detected. Meth was a substantial adulterant in other drugs, e.g. opioids (mean purity 17%).