Despite doctors’ concerns over fueling painkiller addiction, people with a history of drug or alcohol abuse appear more likely than others to be prescribed potentially addictive painkillers for chronic pain, a new study suggests.

The study, published in the journal Pain, looked at the rate of opioid prescriptions for arthritis, lower back injuries and other sources of chronic pain among patients in two large health insurance plans.

Opioids - examples include morphine, OxyContin, and the active ingredient in Percocet - are powerful narcotic painkillers that can become habit-forming. People with a history of substance abuse are not precluded from using the drugs, but guidelines do call for doctors to use caution in prescribing them.

Researchers found that among health-plan patients treated for chronic pain between 1997 and 2005, those with a history of substance abuse were more likely to be prescribed opioids. They also showed an increase in such prescriptions over time.

In one health plan - Kaiser Permanente of Northern California - the prevalence of long-term opioid use increased from roughly 12 percent to 17 percent among patients with past substance abuse problems. Those figures increased from just less than 3 percent to just less than 4 percent, respectively, for patients with no history of drug or alcohol abuse.

The numbers were similar in the second health plan, the Group Health Cooperative in Seattle. There, long-term opioid prescriptions rose from just under 8 percent to nearly 19 percent among pain patients with a history of substance abuse.

Moreover, the study found, opioid prescriptions were far more common among people who had a history of addiction specifically to opiates, such as heroin. Roughly half of these patients in both health plans were prescribed opiates for long-term use - more than 90 days.

The reasons for the findings - including whether some patients were inappropriately seeking opioids - are unknown, according to the researchers, led by Dr. Constance M. Weisner of Kaiser Permanente’s research division in Oakland.

But they speculate that in at least some cases, the prescribing doctor was not aware of the patient’s past substance abuse.

Many of these patients, the researchers note, had their substance abuse problems diagnosed in the health plans’ psychiatry or chemical- dependency programs. Federal law on patient privacy prohibits disclosure of such diagnoses, even on electronic medical records used by other doctors in the same health plan.

Other research has shown that primary care doctors often do not ask patients whether they have ever had alcohol or drug problems, Weisner and her colleagues point out. The current findings, they write, suggest that doctors need to more carefully screen patients for past substance abuse before prescribing opioids.

The question of whether to then prescribe them is more complex. Some argue that patients with a history of substance abuse should not be given long-term opioid therapy, Weisner’s team notes, while others say that most of these patients can use the pain drugs with proper monitoring.

More studies, the researchers conclude, are needed to better understand the risks of prescribing opioids to these patients versus the benefits.

SOURCE: Pain, October 2009.