Introduction The purity, accessibility, and affordability of illicit methamphetamine has increased in recent decades, which has been linked to rising rates of methamphetamine-involved overdoses, psychosis, cardiovascular events, and other health consequences. Nevertheless, information about the quantity of methamphetamine used by regular consumers has been limited, despite the potential clinical utility of exposure quantification.

Methods From August 2024-April 2025, self-reported daily methamphetamine consumption was assessed among n=68 individuals. Methamphetamine samples (n=112) were analyzed for purity using liquid chromatography-mass spectrometry. Percent bioavailability by route of administration and stimulant equivalency were obtained from literature. A simulation model leveraging bootstrapping was used to estimate MOAE.

Results The average reported daily methamphetamine consumption was 0.96g (median 0.36g; range 0.1g-4.0g). Average purity was 71.6% (median 75.5%; range 0.1%-95.0%). Given estimated average bioavailability of 52.0% when smoked, 79.3% when insufflated, 67.2% orally or inserted rectally, and a 2:1 amphetamine-methamphetamine equivalency, the average consumer used 1,549.0 MOAE daily (median 516.6; range 1.3-10,112.0).

Discussion We estimate that consumers of methamphetamine in Los Angeles use a median daily stimulant dose (>500 MOAE) that is nearly tenfold higher than the maximum typical recommended clinical dose of mixed amphetamine salts (60mg). This may help explain the limited efficacy of prescription stimulant treatment for methamphetamine use disorder, which typically employs considerably lower quantities. Given this high dose, these findings shed light on the rising incidence of methamphetamine-related sequalae, such as psychosis, cardiovascular complications, and sudden death. Although exposure quantification is commonplace for alcohol and tobacco use disorders, uncertainties in illicit drug markets has complicated this practice for most illicit drugs. This study supports leveraging emerging information from drug checking programs so that clinicians can approximate exposure quantification.

The authors have declared no competing interest.

The authors report no conflicts of interest. JRF received funding from the National Institute on Drug Abuse (DA049644) and the National institute of Mental Health (MH101072). AJK received educational support through the NIH/National Center for Advancing Translational Science (NCATS) UCLA CTSI (TL1TR001883). CLS received support from the National Institute on Drug Abuse (K01DA050771). This work was supported by the Centers for Disease Control and Prevention as part of Overdose Data to Action: LOCAL (CDC-RFA-CE-23-0003), and made possible through an equipment grant from the James B. Pendleton Charitable Trust to the UCLA AIDS Institute and UCLA Center for AIDS Research. The funders played no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. CLS and JF had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

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The UCLA IRB approved this project (IRB-22-0760) and additionally determined that aspects of this work constituted public health surveillance and not human subjects research.

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