INTRODUCTION: Methamphetamine (MA) use disorder is an important public health concern. MA withdrawal is often the first step in ceasing or reducing use. There are no evidence-based withdrawal treatments, and no medication is approved for the treatment of MA withdrawal. Lisdexamfetamine (LDX) dimesilate, used in the treatment of attention deficit hyperactivity disorder and binge eating disorder has the potential as an agonist therapy to ameliorate withdrawal symptoms, and improve outcomes for patients. METHODS: A single arm, open-label pilot study to test the safety and feasibility of LDX for the treatment of MA withdrawal. Participants will be inpatients in a drug and alcohol withdrawal unit, and will receive a tapering dose of LDX over five days: 250mg LDX on Day 1, reducing by 50mg per day to 50mg on Day 5. Optional inpatient Days 6 and 7 will allow for participants to transition to ongoing treatment. Participants will be followed-up on Days 14, 21 and 28. All participants will also receive standard inpatient withdrawal care. The primary outcomes are safety (measured by adverse events, changes in vital signs, changes in suicidality and psychosis) and feasibility (the time taken to enrol the sample, proportion of screen / pre-screen failures). Secondary outcomes are acceptability (treatment satisfaction questionnaire, medication adherence, concomitant medications, qualitative interviews), retention to protocol (proportion retained to primary and secondary endpoints), changes in withdrawal symptoms (Amphetamine Withdrawal Questionnaire) and craving for MA (visual analogue scale), and sleep outcomes (continuous actigraphy and daily sleep diary). DISCUSSION: This is the first study to assess lisdexamfetamine for the treatment of acute MA withdrawal. If safe and feasible results will go to informing the development of multi-centre randomised controlled trials to determine the efficacy of the intervention.

Background

There are no approved pharmacotherapies for methamphetamine use disorder. Two preliminary phase 2 randomised controlled trials have found mirtazapine, a tetracyclic antidepressant, to be effective in reducing methamphetamine use. The proposed Tina Trial is the first phase 3 placebo-controlled randomised trial to examine the effectiveness and safety of mirtazapine as an outpatient pharmacotherapy for methamphetamine use disorder.

Methods

This is a multi-site phase 3 randomised, double-blind, placebo-controlled parallel trial. Participants are randomly allocated (1:1) to receive either mirtazapine (30 mg/day for 12 weeks) or matched placebo, delivered as a take-home medication. The target population is 340 people aged 18-65 years who have moderate to severe methamphetamine use disorder. The trial is being conducted through outpatient alcohol and other drug treatment clinics in Australia. The primary outcome is measured as self-reported days of methamphetamine use in the past 4 weeks at week 12. Secondary outcomes are methamphetamine-negative oral fluid samples, depressive symptoms, sleep quality, HIV risk behaviour and quality of life. Other outcomes include safety (adverse events), tolerability, and health service use. Medication adherence is being monitored using MEMS® Smart Caps fitted to medication bottles.

Discussion

This trial will provide information on the safety and effectiveness of mirtazapine as a pharmacotherapy for methamphetamine use disorder when delivered as an outpatient medication in routine clinical practice. If found to be safe and effective, this trial will support an application for methamphetamine use disorder to be included as a therapeutic indication for the prescription of mirtazapine.

Trial registration

Australian and New Zealand Clinical Trials Registry ACTRN12622000235707. Registered on February 9, 2022.