Estimating the Daily Milligrams of Oral Amphetamine Equivalent of Illicit Methamphetamine Use

IntroductionThe 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. MethodsFrom 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. ResultsThe 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). DiscussionWe estimate that consumers of methamphetamine in Los Angeles use an average daily stimulant dose (>1,500 MOAE) that is 25-fold 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.