Safety of duloxetine for the treatment of older patients with osteoarthritis knee pain or chronic low back pain

Many people experience chronic pain as they age. Duloxetine is a non-narcotic medication for treatment of chronic pain associated with osteoarthritis of the knee and chronic low back pain as demonstrated in 5 placebo-controlled clinical trials. These studies included 839 duloxetine-treated patients, 237 (28.2%) of whom were aged ≥ 65 years. This post hoc analysis analyzed the safety and tolerability of duloxetine comparing older (≥ 65 years) and younger (18-64 years) patients during12-13 weeks of treatment. Safety was assessed by the frequency rate of ≥5% in treatment-emergent adverse events (TEAEs) for duloxetine that were also significantly higher than placebo; occurrence of serious adverse events (SAE); and significant changes in vital signs or clinical laboratory measures. The duloxetine/placebo differences in each age group were analyzed by a logistic regression model with covariates of treatment, age group, and treatment-by-age group interaction. Statistically significant interaction was defined as p<.10. In each age group, patients taking duloxetine experienced at least 1 TEAE with similar frequency (older, 57.0% vs. younger, 63.3%; p=.91, and there was no significantly greater duloxetine/placebo difference in older patients compared with younger patients for TEAEs that occurred ≥5% with duloxetine and that were significantly higher than placebo. In patients taking duloxetine, the frequency of a TEAE "Fall” was numerically higher in older patients (3, 1.3%) compared with younger patients (3, 0.5%) but without any statistically significant findings. No deaths were reported, and there were no statistically significant increases in SAEs for duloxetine patients compared with placebo in older patients. In summary, no significant treatment-by-age group interactions were observed for any of the safety analyses, which suggest that duloxetine does not present an increased risk for older patients. This work was supported by Eli Lilly and Company.