A team led by Michael Von Korff, ScD, a senior investigator at Group Health Research Institute, studied nearly 10,000 patients who received multiple opioid prescriptions for common chronic pain conditions like back pain and osteoarthritis. Patients who received higher opioid doses were 9 times more likely to overdose than were those receiving low doses. Still, most of the overdoses occurred among patients receiving low to medium doses, because prescriptions at those levels were much more common.
More than 8 million U.S. adults are estimated to be using opioids long-term for chronic pain. The Centers for Disease Control and Prevention (CDC) recently reported that nearly 14,000 U.S. deaths involved prescription opioids in 2006, more than triple the number in 1999. Between 1999 and 2006, nearly 65,000 drug overdose deaths in the United States were reported to involve opioid analgesics.
The team said that this research and the data reviewed cannot determine whether higher doses are a cause of overdose, but he noted that physicians should carefully evaluate and closely monitor patients using opioids long-term.
Previous research had not tracked nonfatal overdoses. "Fatal overdose may be only the tip of the iceberg," said Dr. Von Korff. "For every fatal overdose in our study, 7 nonfatal overdoses occurred, and most of the nonfatal overdoses were medically serious."
Opioid overdose occurred at similar rates across all ages. The overdose events identified were not directly evaluated to assess all potential contributing factors, such as suicide attempts, opioids obtained from nonmedical sources, or accidental or intentional ingestion of more opioid than prescribed.
Although suicide attempts and drug abuse were noted in only a minority of the overdoses in this study, opioid overdoses appeared to occur more often among patients with a history of depression or substance abuse, Dr. Dunn said. Depression tends to be common among chronic pain patients using opioids long-term.
"Nationwide, opioids are widely prescribed long-term for many patients with chronic non-cancer pain," said coauthor Bruce M. Psaty, MD, PhD, a senior investigator at Group Health Research Institute and a professor of medicine, epidemiology, and health services at the University of Washington, where he co-directs the Cardiovascular Health Research Unit. "So a significant opportunity exists to improve safety and the risk-benefit profile through more careful and cautious prescribing."
Citation: Kate M. Dunn et al., Opioid Prescriptions for Chronic Pain and Overdose: A Cohort Study', Ann Intern Med, January 2010, 152:85-92