Many people receiving the most common medication to treat opioid addiction are being prescribed opioid painkillers at the same time, a surprising finding that helps explain why even the most effective substance-abuse therapies don't work nearly as well as experts say they should.

The new study, published Thursday in the journal Addiction, also determined that people tend to stop taking the treatment medication after an average of under two months — far less than the minimum six months or a year that experts say is likely needed for successful recovery.

Both findings illustrate the challenges of  treating drug addiction in a world full of distractions,  temptations, and competing incentives for profit among both patients and physicians.

"We know from other settings that medication-assisted treatment works," said lead author Caleb Alexander, an epidemiologist and codirector of the Center for Drug Safety and Effectiveness at Johns Hopkins Bloomberg School of Public Health. "However, it is a big difference between showing that effect in a clinical trial and showing that effect in the real world."

Researchers analyzed pharmacy data from 11 states, including Pennsylvania, for 38,000 adults who had been prescribed buprenorphine, a maintenance medication that is considered one of the most effective and fastest-growing treatments for opioid addiction, between 2010 and 2012. Buprenorphine, which is a mild opioid, can be prescribed long-term by physicians in their offices, and is intended to prevent withdrawal symptoms during the months or years that the patient works in therapy to gain the skills needed to prevent relapse.

It is  popular because unlike methadone, a stronger maintenance drug, it does not require daily visits to a clinic.

Yet that freedom may be significantly limiting its effectiveness. Nothing forces  patients to attend — or physicians to mandate — behavioral therapy, so patients who don't see progress quickly may quit. Others may continue getting opioid painkillers from other doctors, defeating the purpose of treatment. Or they may sell their painkillers and even their buprenorphine on the street; the maintenance drug is purchased by some addicts to avoid withdrawal symptoms between doses of heroin or stronger pills.

The pharmacy data analyzed for the study showed that 43 percent of patients who were prescribed buprenorphine were getting more powerful opioids at the same time. Most buprenorphine for treatment is prescribed as Suboxone, which includes another drug intended to resist tampering. When Suboxone was analyzed separately, the overlap dropped to 27 percent, which the authors said was still high. On the other hand, the pharmacy data could not include street sales and so likely underestimated the rates of combined use.

Although some opioid painkiller prescriptions during treatment would be for legitimate treatment of pain – and buprenorphine itself is sometimes prescribed for pain – the degree of overlap suggests that multiple prescribers are often involved and some patients may not fully understand the nature of the different drugs, said Adam C. Brooks, who studies the comparative effectiveness of addiction therapies at the Treatment Research Institute in Philadelphia.

The phenomenon the new study illuminates also is part of the "addictive cycle," Brooks said. Patients may think,  "I want to get better but I also don't want to stop using opioids," he said. "Chances are the first stab at treatment isn't going to be enough."

As the nation struggles to rapidly expand inadequate treatment capacity to slow the rising epidemic of overdose deaths, buprenorphine has been seen as the easiest and most effective option. But in many or most cases, the physicians who expand their practices to prescribe the medication, often insisting on cash payment, are not able to provide the kind of "wrangling" — the intensive support, highly structured therapy, and regular testing more commonly associated with methadone clinics — that is necessary for success, Brooks said.

The Wedge Recovery Centers came from the opposite direction. The group of substance abuse and mental health treatment centers had long offered behavioral approaches to treatment. It added medication last year at the request of the Philadelphia Department of Behavioral Health, which has begun insisting that the Medicaid providers it funds show details of how medication and therapy will be used together.

The Wedge requires intensive outpatient therapy —three hours of group learning and therapy three days a week plus individual counseling sessions once a week — and tests urine for compliance every week, said Jason McLaughlin, a licensed clinical social worker and the network's chief operating officer. While 30-day buprenorphine prescriptions that can be picked up at the pharmacy are a big selling point for many patients and doctors elsewhere (a six-month implant was approved last year), the Wedge requires that  medication be picked up at the center. Prescriptions are limited to two weeks and may soon go down  to one week, McLaughlin said, to reduce the temptation to sell the drugs.

Most patients stay in treatment for three or four months, he said — better than what the study found but not long enough by itself to prevent relapse in most cases.

National medical guidelines give no maximum for medication-assisted treatment, saying it should continue until  milestones such as sustained employment and abstinence from drugs of abuse have been reached. Like medications for other chronic conditions like diabetes and high blood pressure, buprenorphine may be given for life.

The goal at the Wedge is one year. "The people that we see that make it all the way through are the most successful," McLaughlin said.