Pharmacoeconomic impact of adverse events of long-term opioid treatment for the management of persistent pain.

Opioids are the most powerful analgesic drugs currently available and consequently form an essential part of the treatment options for malignant and non-malignant chronic pain. However, the benefits of these medications can be offset by gastrointestinal adverse events such as nausea, vomiting and constipation, as well as adverse events affecting the CNS. These occur relatively frequently in patients receiving long-term opioids for pain relief and are a cause of additional patient suffering and reduced work and social functioning, measured as reductions in quality-of-life outcomes. Consequently, adverse events are often the cause of treatment non-compliance or discontinuation (non-persistence). A literature search was conducted using BIOSIS Previews, EMBASE, Cochrane Collaboration and MEDLINE databases to identify references with specific relevance to the measurement of health outcomes related to adverse events of long-term opioid treatment of chronic pain. The results of this search highlighted that clinical interventions required to manage adverse events associated with opioids, and to provide alternative methods of pain control, both incur direct costs. These are largely driven by the cost of medical consults and drug supplies. Indirect costs are generated from work absences and reduced social functioning. Estimated preference ratings, providing an insight into the trade-off between effective pain control and adverse events, have shown that utility decrements associated with an increase in adverse-event severity were similar in size to those caused by a shift from well controlled to poorly controlled pain. Given the rising prevalence of chronic pain conditions (affecting one in five adult Europeans), the direct and indirect costs incurred from the management of adverse events with long-term opioids are likely to be multiplied, contributing to the socioeconomic burden of chronic pain. For this reason, the adverse-event profile of opioid-based analgesics should be improved to achieve more efficient long-term pain control.