The researchers evaluated all sudden cardiac deaths in the Portland area between 2002 and 2006 where detailed autopsies were performed. One group consisted of 22 deaths in which toxicology reports found 1 mg or less of methadone. They compared these cases with 106 in which no methadone was found.
In the first group, 17 of 22, or 77 percent, had no significant cardiac abnormalities and only five had evidence of coronary artery disease. In the control group, 60 percent had identifiable evidence of cardiac disease or structural abnormalities.
"The unexpectedly high proportion of otherwise unexplained sudden deaths in the therapeutic methadone group points to a significant contribution of this drug toward the occurrence of sudden cardiac death among these patients," said Sumeet Chugh, M.D., lead investigator, in a news release.
Sleep Apnea a Risk Also
More than half of the 22 in the first case group were using the drug for pain control, three for drug addiction, three for recreational use and four for an undetermined reason, the researchers found.
The authors noted that they could not rule out sleep apnea as a cause of deaths for some in the methadone group. Others studies have found that methadone prevention programs have increased sleep architecture abnormalities and a higher prevalence of sleep apnea.
Dr. Chugh suggests using additional safeguards before placing patients on methadone, such as an electrocardiogram and assessment of risk for respiratory suppression.
The study was published in the January 2008 issue of The American Journal of Medicine.