Impaired Memory in Subjects Receiving Opioid Agonist Treatment Who Also Abuse Benzodiazepines

Some studies have found impaired memory among subjects receiving opioid agonist treatment (OAT), but this may be partly due to baseline differences between subjects or the effects of other drugs, particularly benzodiazepines. This study tested memory function among Finnish subjects receiving methadone (n=13) or sublingual buprenorphine (n=15) who had concurrent benzodiazepine abuse or dependence and compared them with 15 healthy controls. Memory tests were conducted within 1–2 months of initiating OAT (T1) and repeated 6–9 months later (T2). Comparisons were adjusted for years of education and verbal IQ. Subjects on methadone received a mean daily dose of 73 mg at T1 and 126 mg at T2; those treated with buprenorphine received a mean daily dose of 17 mg at T1 and 23 mg at T2. All subjects receiving OAT also reported abusing a mean diazepam-equivalent dose of 25 mg daily at T1 and T2.

• Subjects in the OAT group performed significantly worse than controls on all memory tests except those related to memory consolidation.

• There was no significant difference in test results between subjects treated with methadone or buprenorphine.

• There was no significant difference in test results between T1 and T2.

Comments:

Prior evidence is clear that benzodiazepines impair memory, but the data on OAT are mixed, and studies have been limited by the fact that many of those included were abusing other substances. These results suggest that people who receive OAT and abuse benzodiazepines have worse memory than healthy people who do not take those medications. But, as with previous studies, it does not sort out how much impairment is due to medications or other causes. It is reassuring that increases in OAT dose over time were not associated with increased memory impairment. These results also suggest that buprenorphine does not offer an advantage over methadone in terms of memory effects, but differences may have been negated by the effect of the benzodiazepines. It should be noted that about one-third of OAT subjects were cannabis users, which may also have affected test performance.

Darius Rastegar, MD

Reference:

Rapeli P, Fabritius C, Kalska H, et al. Memory function in opioid-dependent patients treated with methadone or buprenorphine along with benzodiazepine: longitudinal change in comparison to healthy individuals. Subst Abuse Treat Prev Policy. 2009;4:6.