Clinical trials

In The Netherlands, each year, about 15 thousand people come into treatment because of problems with cocaine use. There is no approved medication for treatment of cocaine addiction and the psychosocial treatment patients receive is not successful for everyone; many return to treatment several times. There is evidence that agonist ("replacement") medications are effective in treating addiction: methadone for heroin addiction; nicotine replacement for smokers. Dexamphetamine is a stimulant medication registered for treatment of ADHD. It may also be effective as agonist treatment for people with cocaine addiction. It will be investigated whether sustained-release dexamphetamine in people with cocaine addiction, participating in routine methadone maintenance treatment for their comorbid opioid use disorder, (1) reduces cocaine use and (2) improves their health and quality of life.

The goal of this clinical trial is to investigate the (cost-)effectiveness of contingency management (CM) compared with Cognitive Behavioural Therapy (CBT) for the treatment of cannabis use disorder (CUD) in youth (16-22 years). The main questions it aims to answer are: * What is the efficacy of 12 weeks outpatient CM versus CBT in youths with a CUD, in terms of cannabis abstinence during the intervention period? * What is the long-term efficacy of CM versus CBT at 6- and 12-months follow-up (FU)? * What is the cost-effectiveness of CM versus CBT at 12-months FU from a societal perspective? Study hypotheses are: 1\. CM will result in more cannabis-abstinent days than CBT during the intervention; 2. CM is more effective and cost-effective than CBT at 12 months follow-up. Eligible patients (n=154) will be randomly assigned to either 12 weeks of outpatient CM or CBT. Assessments are conducted by trained research-assistants at baseline, after 6, 12, 26 and 52 weeks, and twice-weekly during treatment and consist of questionnaires, a computer task and collection of urine samples. Primary endpoint is the number of biochemically verified cannabis abstinent days in the 12-week treatment period. Key secondary endpoint: Treatment response: 50% or more reduction in cannabis use days in the past 4 weeks, compared with baseline. The primary outcome will be modelled in the intention-to-treat population in a (negative binomial) regression analysis with treatment group as independent variable and stratification variables as covariates. Cost-effectiveness and cost-utility analysis (CEA; CUA) will be performed from a societal perspective. CEA: Treatment response is the central clinical endpoint for calculations of incremental costs per responder. CUA: Incremental costs per QALY (based on EuroQoL).