Clinical Trial on the Use of Olanzapine in Reducing the Consumption of Cocaine in Methadone Maintenance Programmes

The consumption of cocaine among people included in Methadone Maintenance Therapy (MMT) is a widely identified phenomenon. but clinical experience and the literature have highlighted the difficulty of finding an effective pharmacological alternative for cocaine abusers. The aim of this study was to assess the use of olanzapine as a therapy for reducing the use of cocaine in MMT while implementing a more controlled design. A randomized clinical trial has been applied to 60 subjects assigned to three MMT programmes. The independent variable was treatment with olanzapine at three dose levels (0, 5 and 10 mg/day), with three treatment groups being formed; they comprised 20, 21 and 19 subjects, respectively. The outcome variable was the percentage of positive urine tests for cocaine consumption, as estimated by means of urine monitoring using immunoassay, during the first three months after the start of treatment. For the data analysis, MANOVA and the hierarchical regression model were used. The mean proportion of previous cocaine consumption was 25.8% (S.D. = 26.4; range 0-100), with no differences between the treatment groups (F((2.57)) = 0.167; p = 0.845). Hierarchical regression analysis showed a significant model in final step (F((5.54)) = 8.61; p <= 0.001), with an explained variance of 44.3% (R(2) = 0.443). The semi-partial correlation coefficients (r) indicated significant effects on the variables: methadone dose (r(s-m) = -0.229), previous cocaine consumption (r(s-m) = 0.345) and treatment with 5 mg/day (r(s-m) = -0.469) and 10 mg/day (r(s-m) = .-0.514) of olanzapine. The mean proportion of positive control results in the untreated subjects was 21%, whereas, in the patients receiving olanzapine therapy, it was 8.8% in those taking a dose of 5 mg/day and 9.5% in those on a dose of 10 mg/day. The prior consumption of cocaine is shown to be a risk predictor for subsequent consumption, whereas an increase in the dose of methadone or treatment with olanzapine both show a protective effect. Specifically, the 10 mg dose of olanzapine, when followed by the 5 mg dose shows the highest degree of explained variance in post-treatment cocaine consumption, after checking the effects induced by the remaining variables.