Researchers also identified a number of risk factors that increase the likelihood of repeat emergency-room visits for overdoses on narcotics -- also known as opioids.
Researchers analyzed data from nearly 20,000 adults in California and Florida who received emergency-room treatment for a narcotic overdose at least once in 2010. They looked at both prescription painkillers such as Vicodin and Oxycontin and illegal drugs such as heroin.
Nearly 7 percent of those patients had two or more emergency-room visits for narcotic overdoses in 2011, with some having as many as five visits, according to the study. About 10 percent of all overdose patients required breathing help with a mechanical ventilator, and the death rate was 1 percent.
In Florida, the cost of emergency-room visits for narcotic overdoses during the one-year follow-up period was $208 million, and 92 percent of that total involved patients with more than one hospitalization, according to the study.
The researchers also found possible patient risk factors associated with repeated emergency-room visits for narcotic overdoses. These included having low income; Medicare or Medicaid coverage; and health problems such as alcohol or drug addiction, psychiatric or neurological conditions, and chronic pulmonary disease.
The study is scheduled for publication in the April issue of the journal Mayo Clinic Proceedings.
"To our knowledge, this is the first study that has identified risk factors for repeat [emergency-room] visits for opioid overdose," lead author Dr. Kohei Hasegawa, of the department of emergency medicine at Boston's Massachusetts General Hospital, said in a hospital news release.
"The dilemma of treating pain appropriately while avoiding opioid-associated adverse events is complicated by insufficient data on those risk factors, and better understanding will help us develop more targeted preventive care," Hasegawa said.
The researchers said increased use of narcotic drugs for pain management led to a 183 percent rise in emergency-room visits for narcotic overdoses in the United States between 2004 and 2011.
The U.S. National Institutes of Health has more about narcotics and pain management.