By Pat Anson, Editor

The difference between controlling chronic pain and risking an opioid overdose can vary widely from patient to patient, according to a new study that found the threshold for safe prescribing may be lower than many doctors think.

Researchers at the University of Michigan Medical School and the Veteran Administration’s Ann Arbor Healthcare System studied the medical records of 221 veterans who died from accidental opioid overdoses and compared them to an equal number of veterans who took opioids for chronic pain, but did not overdose.

The average dose that the overdose victims had been prescribed was over 70 percent higher than what the comparison group received. The average daily dose for the overdose patients was 98 MEM (morphine-equivalent milligrams), compared to about 48 MEM for those who did not overdose.

But the researchers did not find a specific dose that clearly differentiated between patients at risk and those not at risk for overdose. In fact, some overdose victims had prescriptions for well under 50 MEM daily.

Despite that discrepancy, the researchers recommend lowering the recommended dosage threshold below 100 MEM. Lowering the number of high doses, they say, would help more people than it hurts.

“As the United States grapples with the rising toll of accidental overdoses due to opioids, our findings suggest that changing clinical practices to avoid escalating doses for patients with chronic pain could make a major difference in the number of patients who die,” said first author Amy Bohnert, PhD, an epidemiologist at the University of Michigan.

Bohnert was part of the “Core Expert Group” that helped draft the CDC’s controversial guidelines for opioid prescribing. Two co-authors, Joseph Logan and Deborah Dowell, work at the CDC’s National Center for Injury Prevention and Control, which oversaw the guidelines’ development.

The CDC guidelines recommend that primary care physicians start at the “lowest effective dosage” of opioids and should avoid increasing dosages over 90 MEM. Even a daily dose as low as 50 MEM increases overdose risk, according to the guidelines.

“Avoiding prescribing large doses also has the benefit of reducing the amount of the medications going to patients’ homes that has the potential to be taken by others who live with the patient, like children and teenagers,” said Bohnert. “This is important because an opioid that is a larger dose per pill, compared to a smaller one, is going to be deadly to a child or adult who hasn’t been taking the medication regularly.”

The study, which was funded by the Veterans Administration, is published in the journal Medical Care.

The study was based on the veterans’ medical, pharmacy and death certificate records. It did not include those who died by suicide using opioids, or veterans receiving hospice or palliative care.

Veterans were selected only if they filled a prescription for an opioid medication and had a diagnosis of chronic pain during the years 2002 to 2009. The researchers included veterans who had been prescribed codeine, morphine, oxycodone, hydrocodone, oxymorphone, hydromorphone, fentanyl, meperidine, pentazocine, propoxyphene, or methadone.

Under a federal spending bill passed by Congress and signed into law by President Obama, the Veteran’s Administration is required to follow the “voluntary” CDC opioid guidelines. The VA provides health services to 6 million veterans and their families. Over half of the veterans treated by the VA are in chronic pain.