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Effects of Immediate-Release Opioid on Memory Functioning: a Randomized-Controlled Study in Patients Receiving Sustained-Release Opioids.

Kamboj S K, et al.

Journal: Eur J Pain. 2014: April 3. 22 references.
Reprint: Sunjeev K. Kamboj, Research Department of Clinical, Educational and Health Psychology, University College London, UK.
Email: sunjeev.kamboj@ucl.ac.uk 
Faculty Disclosure: Abstracted by T Newitt, who has nothing to disclose.

Editor's Note:
There have been many controversies about the effects of opioids, both sustained and immediate release on cognition, obviously an important subject for performance of hazardous and high cognitive activities. This study adds another dimension with immediate release opioids to sustained release opioids in cancer patients. Not only was cognition not impaired but, paradoxically, some cognition actually improved possibly as a result of improved pain control; or lightening of depression suggesting again that pain and depression are detrimental to cognition.

Class: Pharmacology: Effects of Immediate-Release Opioid on Memory Functioning in Patients Receiving Sustained-Release Opioids.

It is well known that attention to cognitive functions in patients with chronic pain who are being treated with SR opioids and who may be performing skillful and/or danger-ridden tasks is mandatory. This becomes of even more importance when the addition of IR opioids are prescribed for breakthrough pain. The measurement of reversible cognitive effects has been shown to be demonstrated with memory testing before and after additional opioid prescription. This study records standard memory evaluations of patients with chronic pain who were managed with SR and IR opioids.This was a randomized, placebo-controlled, double blind, crossover design used in the comparison of the effects of a single dose of IR opioid with those of a match placebo in patients receiving SR opioids.Twenty (18 cancer) patients with chronic pain being treated with SR morphine or oxycodone were selected and randomly divided into two groups, one of which began the study by receiving a dose of their regular IR opioid (taste disguised by pharmacist) and the other receiving placebo. Patients and dispensing physicians were blinded as to group members.Outcomes were: numerical rating scales (NRSs) for pain and mood, the Hospital Anxiety-Depression Scale (HADS), and the results of the memory tests. Before the first dose of the indicated compound, subjects were given their first word pair learning and recall task followed by a prose task. Forty-five minutes after taking the compound, participants completed a second word pair learning with immediate recall task, and a second prose task (Rivermead Behavioral Memory Test – – RBMT: pre-drug story). A filler task of 20 minutes was then given in order to prevent rehearsal. This was followed by a post drug word pair list memory test. After all the memory tests, a delayed recall of pre-and post-drug story test was given and then a final related word pair list using the same instructions as for the first and second word pairs. There was a 48-hour washout between the groups who then underwent the opposite exercise.

Important Points:

"... IR opioid treatment did not seem to result in impairment of immediate or delayed recall of verbal material learned before IR opioid treatment (retrograde amnesic effect) or after (anterograde amnesia effect)." The authors also found that, contrary to previous studies by the authors, there was no difference between groups in pain relief, which may result in the lack of memory impairment. Most surprising was an "enhanced performance on the interference list following IR opioid." The authors also suggest that this conundrum may be due to reduced depressive symptoms, more advanced educational level, and sustained-release opioid levels.

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