Adverse effects of chronic opioid therapy for chronic musculoskeletal pain.

The use of opioids for the treatment of chronic pain has increased dramatically over the past decade. Whether these drugs provide considerable benefits in terms of pain reduction and improved function to balance the risks associated with their use, however, is unclear. Of particular importance to clinicians treating chronic musculoskeletal pain is opioid-induced hyperalgesia, the activation of pronociceptive pathways by exogenous opioids that results in central sensitization to pain. This phenomenon results in an increase in pain sensitivity and can potentially exacerbate pre-existing pain. Opioids also have powerful positive effects on the reward and reinforcing circuits of the brain that might lead to continued drug use, even if there is no abuse or misuse. The societal risk of increased opioid prescription is associated with increased nonmedical use, serious adverse events and death. Patients with chronic musculoskeletal pain should avoid the long-term use of opioids unless the benefits are determined to outweigh risks, in which case, the use of chronic opioids should be regularly re-evaluated.