Low testosterone levels occur five times more often among men who take long-acting instead of short-acting opioids for chronic pain finds researchers.
While it has been known that opioids cause low testosterone in men, this study is the first to show a significant difference in risk between short-acting (immediate release) and long-acting opioids.
The 81 men in the retrospective study were between 26 and 79 years old (median age 51) and were seen in the chronic-pain clinic at Kaiser Permanente's Santa Rosa Medical Center (Calif.) between January 2009 and June 2010.
All of the participants had been on a stable dose of an opioid for at least three months, and none had a previous diagnosis of low testosterone. A larger retrospective study of more than 1,500 male pain patients is currently under way.
Once prescribed primarily to cancer patients, the use of opioid-based medications such as oxycodone (Oxycontin) and hydrocodone (Vicodin) for treating chronic, non-cancer pain has increased dramatically in recent decades.
"For years, doctors have been encouraged to prescribe long-acting opioids rather than short-acting opioids because we believed they were safer, had less abuse potential, and offered more consistent pain control, but no study has ever been able to support this practice," said said Andrea Rubinstein, MD, of the Departments of Chronic Pain and Anesthesiology, Kaiser Permanente Santa Rosa Medical Center.
The study compared the use of short-acting opioids, which immediately release the pain medication and are taken every four to six hours, and long-acting opioids, which slowly release the pain medication and are taken every eight to 12 hours.
A healthy young man should have testosterone levels between 300 and 800 nanograms per deciliter (ng/dL); in this study, low testosterone, also known as hypogonadism, was defined as less than 250 ng/dL. Low testosterone levels have been associated with decreases in muscle mass, bone density (osteoporosis or osteopenia), cognition, mood, libido (sex drive) and general quality of life.
Seventy-four percent of the men on long-acting opioids had low testosterone levels, compared with 34 percent of the men using short-acting opioids. After controlling for daily dosage and body mass index, the study found that the odds of having low testosterone were 4.78 times greater for men taking a long-acting opioid than a short-acting opioid.
Dose was not associated with an increased risk of low testosterone.
The study was published in The Clinical Journal of Pain.