Objective: To evaluate the analgesic efficacy and safety of tramadol 37.5 mg/acetaminophen 325 mg (tramadol/APAP) combination tablets for treatment of chronic low back pain (LBP).
Methods: This 91 day, multicenter, outpatient, randomized, double blind, placebo controlled study enrolled 338 patients with chronic LBP requiring daily medication for > or = 3 months. Patients with at least moderate pain [pain visual analog scale (VAS) with scores > or = 40/100 mm] after washout were randomized to tramadol/APAP or placebo. After a 10 day titration, patients received 1 or 2 tablets QID. Primary outcome measure was final pain VAS score. Secondary measures included pain relief, quality of life and physical functioning, efficacy failure, and overall medication assessments.
Results: In total, 336 intent-to-treat patients received tramadol/APAP (n = 167) or placebo (n = 169). Mean baseline pain VAS score was 67.8. Intent-to-treat analysis showed significantly better mean final pain VAS scores (47.4 vs 62.9; p < 0.001) and mean final pain relief scores (1.8 vs 0.7; p < 0.001) for tramadol/APAP than for placebo. Roland Disability Questionnaire scores and physical-related subcategories of the McGill Pain Questionnaire and the Medical Outcome Study Short Form-36 Health Survey were significantly better for tramadol/APAP patients. More patients rated tramadol/APAP as "very good" or "good" than placebo (63.6 vs 25.2%; p < 0.001). Kaplan-Meier estimates of cumulative discontinuation rates due to efficacy failures were 22.9% (tramadol/APAP) vs 54.7% (placebo; p < 0.001). The most common treatment related adverse events with tramadol/APAP were nausea (12.0%), dizziness (10.8%), and constipation (10.2%). Average daily dose of tramadol/APAP was 4.2 tablets (tramadol 158 mg/APAP 1369 mg).
Conclusion: Tramadol 37.5 mg/APAP 325 mg combination tablets show efficacy in pain reduction, in measures of physical functioning and quality of life, and in overall medication assessments, with a tolerability profile comparable with other opioids used for the treatment of chronic LBP.