Of the patients taking the mixtures, two-thirds were being prescribed the drugs by two or more doctors, and nearly 40 percent filled their prescriptions at more than one pharmacy, which could be a sign of poor coordination of medical care or an indication that a patient was shopping around for a doctor willing to prescribe a drug inappropriately, Dr. Stettin said.

“It begs for the use of active monitoring and also for better coordination of care,” he said.

Dr. Andrew J. Kolodny, chief medical official of Phoenix House, a drug treatment organization, said that the drop in overall opioid prescribing was a good sign. However, he said he was disturbed that doctors were continuing to give opioids to many patients for long periods of time.

“It suggests that we still have a lot more work to do in better informing the medical community that opioids may not be safe or effective for long-term chronic pain,” said Dr. Kolodny, who has been critical of opioid prescribing practices.

Most experts now believe that while helpful in treating pain from injuries and surgery, opioids should be discontinued as quickly as possible. However, the Express Scripts study found that a large percentage of patients, nearly half, who took an opioid for 30 days or more continued to use the drug long term. Dr. Stettin said patients with chronic pain should be receiving longer-acting drugs that work round the clock. But the study found that about half of those patients were taking short-acting opioids.

“It’s just not the proper way to manage chronic pain,” he said. “That’s a red flag that they are either not being managed correctly, or something else is going on.”

Other aspects of the report mirrored previous research on opioid painkillers. Their use is more prevalent among women and the elderly. Opioid use also varies greatly by geography: people in the Southeast — particularly those living in small cities in Kentucky, Alabama, Georgia and Arkansas — tended to use opioids in greater concentrations than in other regions of the country, especially large cities.

Dr. Stettin said he was heartened that overall use of opioids had fallen, especially for people using them to treat short-term ailments.

Given their addicting potential, he said, “It’s our hope that physicians remain reluctant to start people on an opioid pain medication when they’re not necessary, and that there’s an increase in public awareness that people shouldn’t want to get involved with these medications if they don’t need them.”