During the time, buprenorphine, often sold under the brand name Suboxone, has become an increasingly popular tool to treat opioid addicts, by eliminating their withdrawal symptoms. About a quarter of the 2.8 million people or so people diagnosed with opioid abuse disorder take buprenorphine, typically in oral form.
But only about 2 percent of the nation's doctors are authorized to prescribe the drug, and only about one-fifth of those waivered doctors write around 90 percent of all buprenorphine prescriptions.
The low rate of authorized doctors, and a 100-patient maximum cap on the number of patients an authorized doctor can treat, have been blamed for preventing wider use of buprenorphine, even in the face of evidence that opioid addicts are much less likely to relapse if they are placed on medication to manage their addiction.
In response to those concerns, the federal government this summer raised the maximum cap to 275 patients a single physician can treat with the drug. Since July, 1,275 practitioners have applied for and been approved for the new maximum, federal officials said Monday.
However, the Rand Corp. study released Tuesday suggested that even the doctors allowed to prescribe buprenorphine aren't coming close to the number of patients they could be treating.
The study, published in the Journal of the American Medical Association, found that from 2010 to 2013 more than 20 percent of the doctors authorized to prescribe buprenorphine to opioid addicts were treating three or fewer patients with that drug. And fewer than 10 percent of such doctors were treating more than 75 patients.
The research also found that the median number of opioid addicted patients being treated by an authorized doctor with buprenorphine is often 11 or even fewer patients in 5 of the 7 states with the most physicians with such waivers. In California, the median number of patients was just seven for authorized doctors.
Those medians are well below the 30-patient cap that doctors initially faced when they were authorized to prescribe the medication. And it's much lower than the 100-patient maximum that until this summer was the limit for doctors who applied for that new cap after holding a buprenorphine waiver for at least a year
"We were rather surprised to see such a large number of physicians treating relatively few patients," said Dr. Bradley Stein, senior physician scientist at Rand, and senior author of the study. "We were really surprised that slightly more than 20 percent ... are treating only three or fewer patients per month."
"They certainly are not prescribing to what might be their capacity," he said.
Stein said he and his fellow authors also were surprised by the study's findings that the median duration for buprenorphine treatment per patient was just 53 days.
That was "lower than expected given clinical recommendations of maintenance treatment for up to 12 months and evidence linking longer treatments to better outcomes," the study said.
Novice prescribers cited insufficient access to doctors with more experience prescribing buprenorphoine as well as "insufficient access to substance-abuse counseling for patients" as "barriers to treating more patients" in their own practice, Stein said.
He said that programs that offer mentoring to those doctors with less experience prescribing buprehnorphine and web-based or telephone counseling for patients might be ways to address those concerns, and increase prescription levels.