ASSESSMENT OF COGNITIVE FUNCTIONS IN PATIENTS UNDER MAINTENANCE TREATMENT WITH METHADONE OR BUPRENORPHINE

Background and Aim : Methadone, a full µ- opioid receptor agonist, and buprenorphine, a partial -µ receptor agonist and k-receptor antagonist with a long duration of action, are widely used for the treatment of opioid dependence .Cognitive impairment in drug-dependent patients receiving methadone or buprenorphine has been reported previously. It has been discussed whether buprenorphine treatment may cause less cognitive impairment in comparison with methadone. Very few studies have compared the effects of methadone and buprenorphine on cognition. The aim of present study was to evaluate cognitive performance in methadone- maintenance patients (MMP) and buprenorphine- maintenance patients (BMP) and compare to those healthy controls.Methods : In this cross- sectional study 90 subjects matched for age, gender, education and employment status were categorized into three subgroups: MMP (n= 30), BMP (n= 30) and healthy subjects (n=30). A neuropsychological tests were administered to measure executive function, selective attention and learning/ memory using Stroop test, Wisconsin Card Sorting test (WCST) and Wechsler working memory test (WWMT).Results : : In general, the control group achieved better results than the MMP and BMP groups in most cognitive domains, indicating cognitive impairment in the patients under substitution treatment. BMP group performed better than MMP in Stroop test. The score of WCST was higher in MMP, however the difference was not statistically significant. Scores on WWMT were similar for MMP and BMP groups whereas healthy subjects had significantly higher scores.Conclusion : Our results indicate cognitive impairment in patients receiving methadone and buprenorphine. In addition, treatment with buprenorphine may result in less impairment of cognitive functions compared to treatment with methadone.

Keywords:

Opioid , Methadone , Buprenorphine , Cognitive functions