Lisdexamfetamine in the treatment of methamphetamine dependence: A randomised, placebo-controlled trial

Aims: This study tested the efficacy and safety of a 12-week course of lisdexamfetamine in reducing methamphetamine use, an outcome which is associated with improvements in health and wellbeing, in people dependent on methamphetamine. Design, setting and participants: This study was a randomised double-blind placebo-controlled trial conducted in six specialist outpatient clinics in Adelaide, Melbourne, Newcastle and Sydney, Australia (2018-2021). Participants were164 adults with methamphetamine dependence, reporting at least 14 use days out of the previous 28 days (62% male, 38% female, < 1% other; mean age 39 years). Interventions: Participants were randomly allocated 1:1 to a 15-week regimen of lisdexamfetamine (1-week induction to 250 mg, 12-week maintenance regimen, 2-week reduction; n = 80) or matched placebo (n = 84), followed-up to Week 19. Measurements: The primary efficacy measure was past 28-day methamphetamine use at Week 13. Safety was assessed by adverse event rates. Secondary measures included methamphetamine use during the 12-week treatment period and treatment satisfaction. Findings: Nine randomized participants did not start treatment (five were allocated to lisdexamfetamine and four allocated to placebo) and were excluded from the analyses. Fifty-seven per cent of participants were retained on study medication to primary end-point. There was only weak evidence of a lisdexamfetamine benefit at 13 weeks [adjusted difference in days of methamphetamine use = 2.2, 95% confidence interval (CI) = -0.5 to 5.0; P = 0.49]. However, throughout the whole 12-week treatment maintenance phase, the lisdexamfetamine group had fewer days of methamphetamine use in total (difference = 8.8, 95% CI = 2.7-15.0; P = 0.005). The lisdexamfetamine group reported greater self-reported treatment effectiveness [odds ratio (OR) = 2.89, 95% CI = 1.67-5.02; P < 0.001] and treatment satisfaction (OR = 3.80, 95% CI = 1.93-7.47; P < 0.001). Adverse events with lisdexamfetamine included nausea. Serious adverse events occurred in four (5%) of participants who received lisdexamfetamine. Conclusions: Lisdexamfetamine appears to reduce methamphetamine use over a 12-week treatment period, although there is only weak evidence that reduced use is maintained during the last 4 weeks.