Oxymorphone extended release for the treatment of chronic low back pain: A retrospective pooled analysis of enriched-enrollment clinical trial data stratified according to age, sex, and prior opioid use

Abstract Objective: This study assessed the potential effects of age, sex, and prior opioid use on the response to oxymorphone extended release (ER) in patients with moderate to severe chronic low back pain. Methods: Combined data from 2 placebo-controlled clinical trials with an enriched-enrollment, randomized-withdrawal design were analyzed. In patients aged ≥18 years with chronic low back pain, the dose of oxymorphone ER was titrated to a stable, tolerable, effective dose. Patients who completed titration were randomly assigned to a 12-week double-blind study period with oxymorphone ER or placebo. Oxymorphone immediate release 5 mg was permitted q4-6h, as needed for rescue medication or withdrawal symptoms, for 4 days after randomization and restricted to 10 mg/d thereafter. Pain intensity (100-mm visual analog scale [VAS]; 0 = no pain to 100 = worst pain imaginable) and time to study discontinuation due to lack of efficacy were compared with stratification by age (