Tuesday, September 2, 2008
Pain Medicine has a trial looking at cognitive changes when transitioning chronic non-malignant pain patients from short-acting to long-acting opioids. It involved ~120 adults on short acting opioids (over 80% were on 60mg/day of oral morphine equivalents or less) who were transitioned to approximately equivalent doses of sustained-release morphine (once daily formulation). (Curiously, methadone was treated as a short acting opioid in this study.) They looked at pain, depressive symptoms, and cognitive function (using things like the digit span test) before and after the rotation to once-daily morphine and found that everything got a little better (pain/depressive symptoms) or stayed the same (cognitive functioning). So hooray for once daily morphine.
The problem however is that ~40 patients were deemed 'non-evaluable' (yes, a 3rd of the cohort!) and the outcomes were only presented for those 'evaluable' patients (and it's unclear what happened to those non-evaluable patients or why they were non-evaluable): so the message is I guess that your opioid-tolerant patients who tolerate/go along with 1 month of a rotation to once-daily morphine...well, that they tolerate once-daily morphine.
This was an industry-sponsored study which didn't really go into why they 'lost' a third of their study group (which happens sometimes we all realize but not even telling us why/how really makes you question everything about the study). Especially since the world doesn't necessarily need more proof that many opioid-tolerant patients tolerate opioids (!) - but understanding more about how/why some patients do not tolerate a switch to equivalent doses of a long-acting morphine - that's something we do need to understand better.