Duloxetine in Osteoarthritis (OA) Pain

This study and the hypotheses to be tested arise from work done in our group evaluating brain cortical changes in people with chronic back pain. These studies demonstrated a loss of about 1.5 cc of neocortical gray matter per year of living with the condition, not including gray matter lost due to aging. Since this original publication, more than ten studies have replicated this basic result, showing that distinct chronic pain conditions are associated with specific brain anatomical reorganization, characterized by regional decreases in grey matter density. Recently, other studies have shown that when chronic pain is completely reversed, these anatomical changes seem to at least partially reverse within the time span of 4-12 months, providing evidence for a time window for reversal of grey matter abnormalities A fundamental question that arises from these recent studies is the extent of reversibility of the brain atrophy associated with chronic pain following continuous use of a pain-relieving drug. Apkarian's lab has generated strong evidence that the brain anatomy of subjects with osteoarthritis (OA) is dramatically different from that of healthy subjects. Given that recent data show that hip replacement OA reverses brain atrophy, the investigators can now hypothesize with greater confidence that an effective analgesic should also reverse at least some of the brain atrophy observed in OA. Thus, a study in patients with chronic knee OA treated with duloxetine provides a unique opportunity to answer this question. Since OA patients in this study will have a single new agent for four months, one can directly examine the effects of treatment in relation to progression or regression of brain atrophy. One can also examine whether or not a placebo, which is thought to reflect attentional and motivational states, affects changes in atrophy, and if so, to what extent.

The investigators consider the brain atrophy in chronic pain to be an overall marker of the extent of nervous system reorganization a subject has developed while living with the condition. Animal models of various chronic pain conditions repeatedly provide evidence for this idea, showing, for example, dramatic changes in the way pain is processed in the periphery, the spinal cord, and at the level of individual neurons. The investigators presume that these changes are the same ones contributing to atrophy in human chronic pain. However, most of underlying mechanisms remain to be uncovered. In addition, humans suffering from chronic pain exhibit a large number of cognitive and emotional deficits. The investigators presume that these deficits are directly related to the brain atrophies discovered in chronic pain conditions. Unfortunately, there are no direct studies linking brain regional atrophies to cognitive abilities in chronic pain, although such preliminary studies are underway in Apkarian's lab. Thus, in addition to the answering the previous questions, the present study will also allow us to investigate the extent to which reversing atrophy corresponds to reversing plasticity at multiple levels in the nervous system, as well as whether such reversal also corresponds to improvements in cognitive and emotional abilities.