Severe nonmalignant pain affects a large proportion of adults. Optimal treatment is not clear, and opioids are an important option for analgesia. However, there is relatively little information about the comparative safety of opioids. Therefore, we sought to compare the safety of opioids commonly used for nonmalignant pain.
We devised a propensity-matched cohort analysis that used health care utilization data collected from January 1, 1996, through December 31, 2005. Study participants were Medicare beneficiaries from 2 US states who were new initiators of opioid therapy for nonmalignant pain, including codeine phosphate, hydrocodone bitartrate, oxycodone hydrochloride, propoxyphene hydrochloride, and tramadol hydrochloride; none had a cancer diagnosis, and none were using hospice or nursing home care. Our main outcome measures were incidence rates and rate ratios (RRs) with 95% confidence intervals (CIs) for cardiovascular events, fractures, gastrointestinal events, and several composite end points.
We matched 6275 subjects in each of the 5 opioid groups. The groups were well matched on baseline characteristics. The risk of cardiovascular events was similar across opioid groups 30 days after the start of opioid therapy, but it was elevated for codeine (RR, 1.62; 95% CI, 1.27-2.06) after 180 days. Compared with hydrocodone, after 30 days of opioid exposure the risk of fracture was significantly reduced for tramadol (RR, 0.21; 95% CI, 0.16-0.28) and propoxyphene (0.54; 0.44-0.66) users. The risk of gastrointestinal safety events did not differ across opioid groups. All-cause mortality was elevated after 30 days for oxycodone (RR, 2.43; 95% CI, 1.47-4.00) and codeine (2.05; 1.22-3.45) users compared with hydrocodone users.
The rates of safety events among older adults using opioids for nonmalignant pain vary significantly by agent. Causal inference requires experimental designs, but these results should prompt caution and further study.