Higher-dose pain prescriptions linked to higher overdose risk

Patients who were prescribed higher doses of opioid medications for the treatment of chronic pain were nine-times more likely to overdose on the drugs than were patients placed on the lowest doses of these commonly prescribed pain relievers, Group Health researchers have found.

The study, which appears in the current issue of the journal Annals of Internal Medicine was led by Dr. Michael Von Korff, a senior investigator at Group Health Research Institute.

Use of opioid-containing medications, sold under such brand names as Vicodin, Oxycontin and Duragesic, has gone up more markedly in recent years, and today, 3 percent of U.S. adults, roughly 8 million people, are taking opioid medications for the treatment of chronic non-cancer pain, such as low-back and neck pain, arthritis and menstrual pain.

Overdose rates soar

During the same period the number of overdose deaths linked to prescribed opioids has climbed nearly to 14,000 a year.

In many cases, these overdoses involved abuse of prescription drugs that had been obtained illegally, but not all—and the Group Health researchers wanted to find out what was the risk of overdose among patients for whom opioid drugs are prescribed for noncancer pain.

In the study, the researchers reviewed the Group Health pharmacy records for patients with chronic noncancer pain who had filled at least three opioid prescriptions over a three-month period.

The records were “de-identified” to protect the patient privacy.

All told, the researchers found nearly 10,000 patients receiving such prescriptions. Of these, 51 had at least one overdose during the study period.

In six of these cases, the overdoses were fatal, while the rest were serious enough to cause such consequences as loss of consciousness or hospitalization.

In most the cases the overdoses were accidental, but in six the drugs were taken in a suicide attempt. In a number of cases, the patients had a history of drug abuse or were suspected of drug abuse.

The researchers found that patients who were at highest risk of overdose were those who were been prescribed the highest doses.

Among these high-dose patients, who were prescribed 100 mg. or more a day, the annual rate of overdose was nearly 2 percent, nine times the rate seen among patients prescribed lowest doses, less than 20 mg. a day.

The researchers could not determine whether the risk was increased among higher-dose patients simply because there were being given more potent prescriptions or because there are differences between patients taking higher doses and those taking lower doses that make them more likely to overdose.

Tip of the iceberg?

One of the lessons of the study, said Dr. Von Korff, is that doctors should carefully evaluate and monitor patients who are using opioids long-term.

The other is that non-fatal overdoses may be a much bigger problem than previously realized. Previous studies, Dr. Von Korff noted, collected data on fatal overdoses but not on nonfatal overdoses.

“Fatal overdose may be only the tip of the iceberg,” he said. “for every fatal overdose in our study, seven nonfatal overdoses occcured, and most of the nonfatal overdoses were medically serious.”

To learn more:

• Visit the Web page of the Group Health Research Institute.
• Read the article and related material in Annals of Internal Medicine (subscription or fee required).

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