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

Abstract

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.

Keywords: Abuse liability; Alcohol; Behavioral economics; Blinded-Dose Purchase Task; Cocaine; Demand curve; Drug use; Human; Methamphetamine; Purchase task; Unit price.

Fig. 1.

Left panel: Blinded-Dose Purchase Task demand curves for active and placebo doses across the cocaine (top), methamphetamine (middle), and alcohol (bottom) studies. Error bars represent standard error of the mean. Consumption data plotted as a function of price per dose (rather than unit price; see text for additional comparisons based on unit price). Right panel: demand intensity (left y-axis) and α values (right y-axis) across the cocaine, methamphetamine, and alcohol studies. These indices are depicted following square root and natural-log transformations, respectively. All error bars represent standard error of the mean, *p ≤ .05; **p ≤ .01; ***p ≤ .001. Note. For all studies, the high proportion of cases with zero consumption in placebo conditions did not allow for the determination of elasticity parameters. Therefore statistical comparisons of elasticity were restricted to comparison between active doses, which was only possible in the cocaine and methamphetamine studies