Design
This trial used a randomised, placebo-controlled, counterbalanced, double-blind, four-way within-subjects design with a minimum washout period of 1 week between study visits. Each participant received 0.42 mg/kg methamphetamine and vodka drink (with matched placebo capsule or drink) in a randomised order. Study visits occurred at the same time each week to control for any circadian variation in performance. Order of administration and treatment combination was determined via computer-generated randomisation software. Researchers conducting the study were blinded and were not involved in generating the randomisation schedule nor allocating participants to different drug conditions. The study was registered on the Australian New Zealand Clinical Trials Registry (ACTRN: 12618000629235) and was approved by the Swinburne University Human Research Ethics Committee (HREC: 20210770-8822).