Less impairment on one portion of a driving-relevant psychomotor battery in buprenorphine-maintained than in methadone-maintained patients - Results of a randomized clinical trial

Background: Cognitive impairment in drug-dependent patients under methadone maintenance treatment has been reported before. We assessed whether patients under buprenorphine, a partial mu-opioid agonist, perform better in cognitive tests measuring psychomotor performance as described in previous nonrandomized studies. Methods: We performed a randomized clinical trial in 62 drug-dependent patients under either buprenorphine or methadone treatment. Sixteen patients dropped out of maintenance therapy, before the testing was performed, after 8 to 10 weeks of treatment. Several subtests of the Act & React Test System test battery were used measuring visual perception, selective attention, vigilance, reactivity, and stress tolerance. Findings: Although there were no differences in cognitive function at baseline, patients under buprenorphine treatment showed partially better results in some of the domains tested. The used tests are relevant when assessing driving ability. There was a significant correlation between dose of buprenorphine and some test results. We also found a correlation between age and reaction time and between duration of opioid dependence and results in some subtests. Interpretations (Conclusions): When comparing both treatments in drug dependent patients, buprenorphine produces partially less impairment on cognitive functions in some of the subtests of the psychomotor battery than methadone. This difference is specially relevant when it comes to driving ability and social functioning.