What Dose of Methamphetamine Do Regular Consumers Use Daily? Estimating Milligrams of Oral Amphetamine Equivalent

Abstract

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 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.

Introduction

The purity, accessibility, and affordability of illicit methamphetamine has increased in recent decades¹. This has been linked to rising rates of methamphetamine-involved overdoses, psychosis, psychiatric hospitalizations, cardiovascular events, and other health consequences^2–4. Nevertheless, information about the actual quantity of methamphetamine used in practice, among people with methamphetamine use disorder, has been limited. This is largely due to the historical difficulty in assessing the purity of illicit substances used by patients. Nevertheless, there is considerable potential clinical utility of exposure quantification, such as understanding how a patient’s methamphetamine habit compares to potential replacement doses of prescription stimulants, or assessing the health impacts of dose reductions in illicit stimulant use.

Using recent advancements in drug checking technologies and services, we quantify the purity of methamphetamine samples used by regular consumers in Los Angeles. We combine this with self-reported daily consumption quantities among the same population to estimate the daily Milligrams of Oral Amphetamine Equivalent (MOAE). This quantity is likely to be more easily interpretable by psychiatrists and other clinicians, who are familiar with dosing of mixed amphetamine salts, rather than the quantity of illicit methamphetamine, for which dosing depends on drug concentration, route of administration, and bioavailability.

Methods

Daily MOAE was estimated according to Equation 1, where Consumption is the daily milligrams of illicit methamphetamine used, Purity is the proportion of active compound in substances sold as illicit “methamphetamine”, Bioavailability is the route-of-administration-specific proportion of total drug used that is absorbed systemically, Methamphetamine: Amphetamine Equivalence is the ratio of physiological potency between methamphetamine and mixed amphetamine salts, and Bioavailability Oral Amphetamine Salts is the fraction of mixed amphetamine salts that is absorbed systemically when taken orally.

Equation 1.

Calculation of estimated mg of oral amphetamine equivalent (MOAE) self-administered among regular consumers in Los Angeles

$$\mathit{\text{Milligrams}}\mathit{\text{of}}\mathit{\text{Oral}}\mathit{\text{Amphetamine}}\mathit{\text{Equivalence}}(\mathit{\text{MOAE}})=\mathit{\text{Consumption}}\cdot \mathit{\text{Purity}}\cdot \mathit{\text{Bioavailability}}\cdot \mathit{\text{Methamphetamine}}:\mathit{\text{Amphetamine}}\mathit{\text{Equivalence}}\cdot \frac{1}{\mathit{\text{Bioavailability}}\mathit{\text{Oral}}\mathit{\text{Amphetamine}}\mathit{\text{Salts}}}$$

To estimate the distribution of MOAE combining uncertainty and variation in each of the aforementioned parameter inputs, we employed a bootstrapping approach leveraging 10,000 draws. This allows for the inclusion of uncertainty in each parameter, which is propagated through to the final estimated MOAE.

Methamphetamine purity by weight was assessed using liquid chromatography-mass spectrometry (LC-MS) among n=112 samples collected at a community-based drug checking program in Los Angeles County⁵. Samples were limited to those sold as methamphetamine, and for which clients expected only methamphetamine. Daily methamphetamine consumption volume and route of administration was assessed by self-report using a survey among n=68 individuals who regularly consume methamphetamine and brought samples for testing. Bioavailability by route-of-administration and stimulant equivalency factors were drawn from literature review (see supplemental methods). 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.

Results

The average reported daily methamphetamine consumption was 0.96g (Figure 1). A skewed distribution was observed with a median of 0.36g. The range was 0.1g-4.0g daily. Estimated mean and median purity was 71.6% and 75.5%, respectively, with a range from 0.1% to 95.0%.

Figure. Distributions, Median, and Mean Grams per Day Consumed, Percent Concentration (Purity), and Estimated mg of Oral Amphetamine Equivalent Self-Administered Among Regular Consumers in LA.

For each panel, a dashed vertical line shows the distribution mean, and a dashed solid line shows the distribution mean. Left: The distribution of self-reported grams of methamphetamine ingested per day among regular consumers participating in drug checking services in Los Angeles. Center: Percent concentration (purity) of expected methamphetamine samples provided by clients at drug checking services in Los Angeles. Right: the estimated distribution of milligrams of oral amphetamine equivalent (MOAE) consumed among drug checking clients in Los Angeles.

Bioavailability was estimated from literature sources describing experimental data using human subjects (see supplemental methods for a full description). Average bioavailability of smoked methamphetamine was estimated at 52.0% (of the total “pipe dose”), reflecting a uniform distribution with a minimum of 37% and a maximum of 67%. Bioavailability of insufflated “snorted” methamphetamine was modeled using a normal distribution with a mean of 79.0% and a standard deviation of 6.7%. Oral bioavailability was estimated using a normal distribution with a mean of 67.2% and a standard deviation of 1.59%. Rectal bioavailability was estimated using a normal distribution with a mean of 67.2% and a standard deviation of 20.0%. The amphetamine-methamphetamine equivalency was estimated to be 1:2.

Given the above factors, the estimated mean and median MOAE used daily was 1,549.0 and 516.6, respectively. The estimated range was 1.3 MOAE to 10,112.0 MOAE daily.

Discussion

We 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 quantities⁶. For instance, the 60 to 110mg daily used in trials of amphetamine salts for methamphetamine use disorder would represent 1/14^th to 1/25^th of the average estimated methamphetamine usage observed in our population^7,8.

Given this high dose, these findings also shed light on the rising incidence of methamphetamine-related sequalae, such as psychosis, cardiovascular complications, and sudden death^1,3, which are much more common with illicit methamphetamine compared to the prescribed use of stimulant therapies⁹.

Although exposure quantification is commonplace for alcohol and tobacco use disorders, uncertainties in illicit drug markets has complicated this practice for most illicit drugs. However, this study suggests that by leveraging emerging information from drug checking programs, as well as regularly asking their patients about consumption quantities, clinicians may be able to approximate exposure quantification. This may be useful in understanding the clinical benefits of treatments that result in dose reductions. This can also inform risk stratification for cardiac, psychiatric and other outcomes and personalizing care, including withdrawal management. This approach would also mirror efforts to quantify use and employ usage reduction as a clinical endpoint in addiction-related clinical trials¹⁰.

This study represents an example of how emerging drug checking technologies can provide consumers with information that can empower them to make safer drug use decisions, despite the highly uncertain and rapidly-evolving nature of the illicit drug supply.

This work is limited by its use of data from a single city and may not be generalizable to other contexts. Self-report consumption data is also prone to recall and desirability biases. Although the LC-MS testing technology used here is generally considered the ‘gold standard’ for this type of assessment, it can miss certain contaminants not explicitly tested for.

In sum, we provide the first quantification, to our knowledge, of the daily dose of methamphetamine used by regular consumers. We defined a novel metric, MOAE, which can assist psychiatrists and other clinicians to describe methamphetamine consumption in terms of prescription stimulant equivalent. We find that the average regular consumer uses 25-fold the recommended maximum dose of amphetamine salts, which may explain the myriad and severe health harms observed among patients with long-term methamphetamine use. Further study will be required to assess the degree to which these findings hold true in other populations.