The effect of methamphetamine and heroin price on polydrug use: A behavioural economics analysis in Sydney, Australia

Contextual and psychosocial factors influencing drug reward in humans: The importance of non-drug reinforcement

The reinforcing efficacy, or behavior-strengthening effect, of a substance is a critical determinant of substance use typically quantified by measuring behavioral allocation to the substance under schedules of reinforcement with escalating response requirements. Although responses on these tasks are often used to indicate stable reinforcing effects or trait-level abuse potential for an individual, task designs often demonstrate within-person variability across varying degrees of a constraint within experimental procedures. As a result, quantifying behavioral allocation is an effective approach for measuring the impact of contextual and psychosocial factors on substance reward. We review studies using laboratory self-administration, behavioral economic purchase tasks, and ambulatory assessments to quantify the impact of various contextual and psychosocial factors on behavioral allocation toward consumption of a substance. We selected these assessment approaches because they cover the translational spectrum from experimental control to ecological relevance, with consistent support across these approaches representing greater confidence in the effect. Conceptually, we organized factors that influence substance value into two broad categories: factors that influence the cost/benefit ratio of the substance (social context, stress and affect, cue exposure), and factors that influence the cost/benefit ratio of an alternative (alternative non-drug reinforcers, alternative drug reinforcers, and opportunity costs). We conclude with an overview of future research directions and considerations for clinical application.

The Blinded-Dose Purchase Task: assessing hypothetical demand based on cocaine, methamphetamine, and alcohol administration

RATIONALE

Behavioral economic drug purchase tasks quantify the reinforcing value of a drug (i.e., demand). Although widely used to assess demand, drug expectancies are rarely accounted for and may introduce variability across participants given diverse drug experiences.

OBJECTIVES

Three experiments validated and extended previous hypothetical purchase tasks by using blinded drug dose as a reinforcing stimulus, and determined hypothetical demand for experienced effects while controlling for drug expectancies.

METHODS

Across three double-blind, placebo-controlled, within-subject experiments, cocaine (0, 125, 250 mg/70 kg; n=12), methamphetamine (0, 20, 40 mg; n=19), and alcohol (0, 1 g/kg alcohol; n=25) were administered and demand was assessed using the Blinded-Dose Purchase Task. Participants answered questions regarding simulated purchasing of the blinded drug dose across increasing prices. Demand metrics, subjective effects, and self-reported real-world monetary spending on drugs were evaluated.

RESULTS

Data were well modeled by the demand curve function, with significantly higher intensity (purchasing at low prices) for active drug doses compared to placebo for all experiments. Unit-price analyses revealed more persistent consumption across prices (lower α) in the higher compared to lower active dose condition for methamphetamine (a similar non-significant finding emerged for cocaine). Significant associations between demand metrics, peak subjective effects, and real-world spending on drugs also emerged across all experiments.

CONCLUSIONS

Orderly demand curve data revealed differences across drug and placebo conditions, and relations to real-world measures of drug spending, and subjective effects. Unit-price analyses enabled parsimonious comparisons across doses. Results lend credence to the validity of the Blinded-Dose Purchase Task, which allows for control of drug expectancies.

Assessment of demand for methamphetamine and cigarettes among individuals with methamphetamine use disorder

Methamphetamine (MA) is a highly addictive stimulant with recent upward trends in prevalence and associated public health problems. Drug demand, as assessed by hypothetical purchasing tasks, has been useful in addictions research and may help our understanding of the factors influencing MA use. However, no studies have assessed MA demand using current models of demand. The purpose of the current study was to assess demand for MA using a hypothetical drug purchasing task. Given high rates of cigarette smoking among MA users, it was of interest also to assess and compare demand for MA relative to cigarettes. Participants consisted of non-treatment-seeking volunteers with MA use disorder (N = 18), of whom 17 reported daily smoking. Results showed the exponentiated demand model provided a good fit to consumption data. Results from Bayesian generalized linear modeling demonstrated multiple positive relationships (posterior probability ≥75%) between self-reported drug use (days MA used in the past 30 days, cigarettes smoked per day) and indices of demand for each drug (Qo, Omax, Pmax, and break point). Comparing MA to cigarettes, results from Bayesian generalized linear mixed modeling revealed greater abuse liability for MA compared to cigarettes (posterior probability ≥99%) based on α and essential value. Overall, the findings of the current study support the feasibility and validity of the exponentiated demand model for assessing demand for drugs among individuals with MA use disorder. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Behavioral economic demand in opioid treatment: Predictive validity of hypothetical purchase tasks for heroin, cocaine, and benzodiazepines

BACKGROUND

Behavioral economics provides a framework in which to understand choice and motivation in the field of substance use disorders. Hypothetical purchase tasks (HPT), which indicate the amount or probability of purchasing substances at different prices, have been suggested as a clinical tool that can help predict future substance use and identify targets for intervention.

METHODS

Hypothetical demand for heroin, cocaine, and benzodiazepines was assessed at baseline and after six-months in 52 opioid-agonist treatment patients. The results were analyzed using a novel exponential demand equation (normalized zero-bounded exponential model [ZBEn]) that uses a log-like transform that accommodates zero consumption values.

RESULTS

Demand for these drugs was well described by the ZBEn model. After six months, demand intensity for heroin was decreased and demand metrics for cocaine and benzodiazepines increased. Multiple demand curve indices at baseline predicted the percentage of drug-positive urinalysis results at follow-up, even after controlling for covariates. Additionally, participants were divided into High and Low baseline demand groups for each drug based on demand indices. Participants with High demand at baseline for 8 out of 9 groups had significantly more drug-positive urine samples in the subsequent 6-month period.

CONCLUSIONS

This report provides evidence that demand assessment is predictive of future substance use and could help guide treatment planning at intake. These results also demonstrated that the ZBEn model provides good fits to consumption data and allows for sensitive statistical analyses.

Co-use of methamphetamine and opioids among people in treatment in Oregon: A qualitative examination of interrelated structural, community, and individual-level factors

BACKGROUND

Rates of methamphetamine use and methamphetamine-related deaths have increased steadily in the United States in recent years. Methamphetamine is increasingly present in opioid-related deaths. An initial study of de-identified urine specimens (n = 102) collected at a drug treatment program between 2017 and 2018 indicated that 61% of specimens contained methamphetamine; of the specimens containing methamphetamine, people were, on average, five years younger than those who tested negative for methamphetamine; and non-fentanyl opioids were more than three times as common in methamphetamine positive specimens. The National Drug Early Warning System (NDEWS) Coordinating Center initiated a HotSpot Study to assess whether there was an emerging dynamic in the area, or if enhanced data collection could give insights into the co-use of methamphetamine and opioids.

METHODS

A qualitative study, grounded in principles of rapid ethnographic assessment and a social science/anthropological framework was conducted and used methodological complementarity to contextualize results from the initial urinalysis study. Targeted sampling was conducted at two treatment sites. Program staff and patients were recruited to participate in focus groups and semi-structured interviews to assess structural, community, and individual-level factors impacting methamphetamine and opioid co-use.

RESULTS

Within our broader framework of structural, community, and individual-level factors intersecting co-use, our data yielded three sub-themes: 1) the circulation of stigma regarding methamphetamine use was consistently described by both patients and staff and this intersected structural changes in treatment policy and suggested compounded stigma; 2) community-level factors and temporality were important for understanding patterns of methamphetamine use and for further interpreting the initial urinalysis; 3) patient rationales regarding the co-use of methamphetamine and opioids included strategies to mitigate the harms of heroin, as well as to detox or titrate the effects of heroin.

CONCLUSION AND IMPLICATIONS

Using an ethnographically-oriented and social science/anthropological approach and methodological complementarity to contextualize the prior urinalysis study demonstrates how behavioral variables cannot be abstracted from larger socio-structural and community contexts which impact people's decision-making process regarding co-use of methamphetamine and opioids. Further, by grounding our analysis in the meaning-centered and experiential narratives of people who use drugs, our research demonstrates the importance of considering the expertise of people who co-use opioids and methamphetamine as central for informing future sustainable program planning to address co-use that also accounts for the interrelationship between structural, community, and individual-level factors.

One Is Not Enough: Understanding and Modeling Polysubstance Use

Substance use disorder (SUD) is a chronic, relapsing disease with a highly multifaceted pathology that includes (but is not limited to) sensitivity to drug-associated cues, negative affect, and motivation to maintain drug consumption. SUDs are highly prevalent, with 35 million people meeting criteria for SUD. While drug use and addiction are highly studied, most investigations of SUDs examine drug use in isolation, rather than in the more prevalent context of comorbid substance histories. Indeed, 11.3% of individuals diagnosed with a SUD have concurrent alcohol and illicit drug use disorders. Furthermore, having a SUD with one substance increases susceptibility to developing dependence on additional substances. For example, the increased risk of developing heroin dependence is twofold for alcohol misusers, threefold for cannabis users, 15-fold for cocaine users, and 40-fold for prescription misusers. Given the prevalence and risk associated with polysubstance use and current public health crises, examining these disorders through the lens of co-use is essential for translatability and improved treatment efficacy. The escalating economic and social costs and continued rise in drug use has spurred interest in developing preclinical models that effectively model this phenomenon. Here, we review the current state of the field in understanding the behavioral and neural circuitry in the context of co-use with common pairings of alcohol, nicotine, cannabis, and other addictive substances. Moreover, we outline key considerations when developing polysubstance models, including challenges to developing preclinical models to provide insights and improve treatment outcomes.

Reciprocal Substitution Between Methamphetamine and Heroin in Terms of Reinforcement Effects in Rats

Heroin and methamphetamine are both popular illicit drugs in China. Previous clinical data showed that habitual users of either heroin or methamphetamine abuse the other drug for substitution in case of unavailability of their preferred drug. The present study aimed to observe whether heroin can substitute the methamphetamine reinforcement effect in rats, and vice versa. Rats were trained to self-administer heroin or methamphetamine (both 50 μg/kg/infusion) under an FR1 reinforcing schedule for 10 days. After having extracted the dose-effect curve of the two drugs, we administered methamphetamine at different doses (12.5-200 μg/kg/infusion) to replace heroin during the period of self-administration, and vice versa. The heroin dose-effect curve showed an inverted U-shaped trend, and the total intake dose of heroin significantly increased when the training dose increased from 50 to 100 or 200 μg/kg/infusion. Following replacement with methamphetamine, the total dose-effect curve shifted leftwards and upwards. By contrast, although the dose-effect curve of methamphetamine also showed an inverted U-shaped trend, the total dose of methamphetamine significantly decreased when the training dose decreased from 50 to 25 μg/kg/infusion; conversely, when the methamphetamine training dose increased, the total dose did not change significantly. The total dose-effect curve shifted rightwards after heroin was substituted with methamphetamine. Although heroin and methamphetamine had their own independent reward effects, low doses of methamphetamine can replace the heroin reward effect, while high doses of heroin can replace the methamphetamine reward effect. These results demonstrated that heroin and methamphetamine can substitute each other in terms of reinforcement effects in rats.

Assessing the longitudinal stability of latent classes of substance use among gay, bisexual, and other men who have sex with men

BACKGROUND

Association between substance use and HIV-risk among gay and bisexual men (GBM) is well documented. However, their substance use patterns are diverse, and it is unknown whether self-reported use patterns are stable over time.

METHODS

Sexually-active GBM, aged >16 years, were recruited in Metro Vancouver using respondent-driven sampling and followed across 5 study visits at six-month intervals (n = 449). To identify distinct patterns of substance use and their longitudinal stability, Latent Transition Analysis (LTA) was conducted for drugs reported by at least 30 participants. Intraclass correlation coefficients (ICC) quantified the stability of class assignments.

RESULTS

Six classes characterizing 'limited drug use' (i.e., low use of all drugs, except alcohol), 'conventional drug use' (i.e., use of alcohol, marijuana, and tobacco), 'club drug use' (i.e., use of alcohol, cocaine, and psychedelics), 'sex drug use' (i.e., use of alcohol, crystal meth, GHB, poppers, and erectile dysfunction drugs), 'street drug use' (i.e., use of alcohol and street opioids) and 'assorted drug use' (i.e., use of most drugs) were identified. Across five visits (2.5 years), 26.3% (n = 118/449) of GBM transitioned between classes. The prevalence of limited use trended upwards (Baseline:24.5%, Visit 5:28.3%, p < 0.0001) and assorted use trended downwards (13.4%-9.6%, p = 0.001). All classes had strong longitudinal stability (ICC > 0.97).

CONCLUSION

The stability of latent substance use patterns highlight the utility of these measures in identifying patterns of substance use among people who use drugs - potentially allowing for better assessment of these groups and interventions related to their health.

Analysing pseudoephedrine/methamphetamine policy options in Australia using multi-criteria decision modelling

BACKGROUND

In this paper we capture and synthesize the unique knowledge of experts so that choices regarding policy measures to address methamphetamine consumption and dependency in Australia can be strengthened. We examine perceptions of the: (1) influence of underlying factors that impact on the methamphetamine problem; (2) importance of various models of intervention that have the potential to affect the success of policies; and (3) efficacy of alternative pseudoephedrine policy options.

METHODS

We adopt a multi-criteria decision model to unpack factors that affect decisions made by experts and examine potential variations on weight/preference among groups. Seventy experts from five groups (i.e. academia (18.6%), government and policy (27.1%), health (18.6%), pharmaceutical (17.1%) and police (18.6%)) in Australia participated in the survey.

RESULTS

Social characteristics are considered the most important underlying factor, prevention the most effective strategy and Project STOP the most preferred policy option with respect to reducing methamphetamine consumption and dependency in Australia. One-way repeated ANOVAs indicate a statistically significant difference with regards to the influence of underlying factors (F(2.3, 144.5)=11.256, p<.001), effectiveness of interventions (F(2.4, 153.1)=28.738, p<.001) and policy options (F(2.8, 175.5)=70.854, p<.001).

CONCLUSION

A majority of respondents believed that genetic, biological, emotional, cognitive and social factors are the most influential explanatory variables in terms of methamphetamine consumption and dependency. Most experts support the use of preventative mechanisms to inhibit drug initiation and delayed drug uptake. Compared to other policies, Project STOP (which aims to disrupt the initial diversion of pseudoephedrine) appears to be a more preferable preventative mechanism to control the production and subsequent sale and use of methamphetamine. This regulatory civil law lever engages third parties in controlling drug-related crime. The literature supports third-party partnerships as it engages experts who have knowledge and expertise with respect to prevention and harm minimization.

The price elasticity of demand for heroin: Matched longitudinal and experimental evidence

This paper reports estimates of the price elasticity of demand for heroin based on a newly constructed dataset. The dataset has two matched components concerning the same sample of regular heroin users: longitudinal information about real-world heroin demand (actual price and actual quantity at daily intervals for each heroin user in the sample) and experimental information about laboratory heroin demand (elicited by presenting the same heroin users with scenarios in a laboratory setting). Two empirical strategies are used to estimate the price elasticity of demand for heroin. The first strategy exploits the idiosyncratic variation in the price experienced by a heroin user over time that occurs in markets for illegal drugs. The second strategy exploits the experimentally induced variation in price experienced by a heroin user across experimental scenarios. Both empirical strategies result in the estimate that the conditional price elasticity of demand for heroin is approximately -0.80.

How do drug market changes affect characteristics of injecting initiation and subsequent patterns of drug use? Findings from a cohort of regular heroin and methamphetamine injectors in Melbourne, Australia

BACKGROUND

Changes in drug market characteristics have been shown to affect drug use patterns but few studies have examined their impacts on injecting initiation experiences and subsequent patterns of injecting drug use (IDU).

METHODS

We collected data on self-reported injecting initiation experiences and past-month patterns of IDU from 688 regular heroin and methamphetamine injectors in Melbourne, Australia, who initiated injecting across three different drug market periods (prior to the Australian heroin shortage ('high heroin')/immediately following the shortage ('low heroin')/'contemporary' markets (fluctuating heroin and methamphetamine availability)). We used univariable and multivariable logistic regression to examine the relationship between period of injecting initiation and first drug injected, and multinomial logistic regression for the relationship between period of injecting initiation and current injecting patterns.

RESULTS

425 participants (62%) reported initiating injecting in the high heroin period, 146 (21%) in the low heroin period, and 117 (17%) in the contemporary period. Participants who initiated injecting during the low heroin period were twice as likely to initiate injecting using a drug other than heroin (AOR: 1.94, 95% CI: 1.27-2.95). The most common patterns of drug use among study participants in the month preceding interview were polydrug use (44%) and primary heroin use (41%). Injecting initiation period was either non-significantly or weakly associated with current drug use pattern, which was more strongly associated with other socio-demographic and drug use characteristics, particularly self-reported drug of choice.

CONCLUSION

The drug market period in which injecting initiation occurred influenced the first drug injected and influenced some aspects of subsequent drug use. In the context of highly dynamic drug markets in which polydrug use is common there is a need for broad harm reduction and drug treatment services which are flexible and responsive to changing patterns of drug use.

Can price get the monkey off our back? A meta-analysis of illicit drug demand

Because of the increased availability of price data over the past 15 years, several studies have estimated the demand for illicit drugs, providing 462 estimates of the price elasticity. Results from estimating several meta-regressions reveal that these price elasticity estimates are influenced by a number of study characteristics. For instance, the price elasticity differs across drugs, with its absolute value being smallest for marijuana, compared with cocaine and heroin. Furthermore, price elasticity estimates are sensitive to whether demand is modeled in the short-run or the long-run, measures of quantity and price, whether or not alcohol and other illicit drugs are included in the specification of demand, and the location of demand. However, a number of other factors, including the functional form of demand, several specification issues, the type of data and method used to estimate demand, and the quality of the publication outlet, have less influence on the price elasticity.

National-level drug policy and young people's illicit drug use: a multilevel analysis of the European Union

INTRODUCTION

Recent research has called upon investigators to exploit cross-national differences to uncover the cultural and structural factors influencing drug use. While the individual-level correlates are well-established, little is known about the association between cross-national variation in drug policies and young people's substance use. This study examines, net of individual-level predictors, the association between national-level drug policy and use of an illicit drug other than cannabis.

METHODS

The study uses Eurobarometer repeated cross-sectional surveys in 2002 and 2004 of adolescents aged 15-24 drawn in multistage, random probability samples proportional to population size and density within regions of their country (N=15,191). Participants completed self-reported measures of last month drug use, attitudes toward drugs, school and work participation, and demographics. Gathered from several international bodies, national-level policy measures include drug offense levels, possession decriminalization, and presence and usage of harm reduction strategies.

RESULTS

Hierarchical logistic regression models demonstrate that, while controlling for important individual-level predictors, in countries where there is no restriction on possession of drugs for personal use, the odds of drug use in the last month are 79% lower (p<0.05). On the other hand, higher usage of treatment and drug substitution are associated with higher levels of drug use. These results are robust to several alternate specifications.

CONCLUSIONS

Among the strongest and most consistent findings, eliminating punishments for possession for personal use is not associated with higher drug use. The results indicate that researchers should take national-level context into account in individual-level studies of drug use.

Methamphetamine Users’ Perceptions of Exchanging Drugs for Money

Trust, between regular buyers and sellers, is thought to underpin retail-level illicit drug markets, discouraging sellers from taking advantage of buyers. Although dealers report rewarding regular, trusted customers with assured purity, less is known about their customers’ experience of trust. Interviews with 101 methamphetamine users in New South Wales, Australia, confirm that users establish ongoing relationships with dealers. Irrespective of their level of methamphetamine use, some users trust their main dealer to supply a fair deal, whereas others expect to be taken advantage of. The study identified factors other than trust that might regulate dealer behavior. Methamphetamine use ebbs and flows. Users source drugs from multiple dealers, substitute other drugs for methamphetamine, and some buy a range of drugs from the one dealer. Our findings emphasize the complexity of factors that influence decisions about purchasing illicit drugs and point to a more holistic view of what regulates dealer behavior.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).