Combination of buprenorphine and naltrexone in the treatment of cocaine dependence

Gilberto Gerra

G. Gerra, L. Somaini, M. Amore, A. Busse, E. Saenz. United Nations Office on Drugs and Crime, Austria

Preliminary evidence suggests the effectiveness of buprenorphine (BUP), and BUP in combination with naltrexone (NAL), in reducing cocaine consumption among heroin addicts, but such combination has never been used in the treatment of primary cocaine dependence. The objective of the present randomized study was to determine the effectiveness of the combination BUP/NAL in cocaine addiction treatment. BUP and NAL were combined during a 12-week protocol, theoretically cancelling the μ-opioid effects of the partial agonist medication. Twenty patients (Group A) received NAL (50 mg oral dose) plus placebo. Alternatively, 20 patients (Group B) received NAL (50 mg oral dose) plus BUP (10–16 mg sublingual) for the 12 weeks of the study. The end points of the study were retention in treatment, negative urinalyses, changes in psychological symptoms (Symptom Checklist-90 Revised [SCL-90]), and craving scores (visual analysis scale). No significant change in pupillary diameter after BUP administration was evidenced during clinical observations in Group B. Retention rate was not significantly different between groups, which was 45% and 60% for Group A and B, respectively. Patients treated with NAL in combination with BUP showed a 76% lower risk of positive urines compared with patients treated with naltrexone and placebo.

Accordingly, craving scores decreased significantly less in Group A patients than in Group B patients. SCL-90 scores at the end of the study showed a higher level of psychiatric symptoms in Group A subjects than in Group B. Although obtained from a small sample of subjects, findings of the present study seem to indicate a potential role for the non-μ-opioid effects of BUP in the treatment of cocaine dependence. It is difficult to understand at this stage if the positive outcome should be attributed to the antagonist effects of BUP on k-receptors, with possible improvement of mood, or to the agonistic action of the drug on orphanin receptors. In any case, the concomitant use of NAL permitted experimenting in this area without the risk of inducing a secondary opioid dependence in patients primarily addicted to cocaine.

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