Cognitive function during substitution treatment

For many patients substitution therapy provides the stability to initiate life style changes necessary to obtain steady employment and function in society. A critical question is the extent to which drug dependence is associated with impairments in cognitive performance which might affect daily functioning. In our randomized clinical trial 46 opiate dependent patients were randomly assigned to buprenorphin (BUP) (n=22) or methadone treatment (MMP) (n=24). Cognitive performance (attention, concentration, working memory, cognitive speed) was evaluated at baseline during the first week of treatment (t1) and after 8–10 weeks of stable treatment (t2) and compared to a control group that closely matched the clinical group on the variables age, gender and education. BUP and MMP patients under stable treatment reached significantly worse results in trail making test (A and B), Verbal Learning and Memory test, d2– test and some trials of Regensburg Word Fluency test compared to healthy controls. BUP and MMP–group could improve their concentration in d2–test under stable treatment (p<0,001). No major differences between BUP and MMP group were observed under stable treatment. A number of studies before have described cognitive impairment and deficits in MMP patients (for example Darke, S. (2000), Lyvers M (2003), Davis (2002)), but not for BUP patients. Addicts treated with buprenorphine often describe an increased alertness compared to methadone treatment. That could not be objectified in our testings. Our results indicate that Buprenorphine is comparable to methadone in regard to cognitive function. Both groups could improve their concentation in d2–test under stable treatment. There are some limitations to this study basically due to the small number of patients tested and the high number of comorbid substance abuse.