Objective: To examine the efficacy and safety of tramadol/acetaminophen (APAP) for the management of painful diabetic peripheral neuropathy (DPN).
Methods: Adults with painful DPN involving the lower extremities received 37.5 mg tramadol/325 mg APAP or placebo, up to 1-2 tablets four times daily, for 66 days. Subjects rated average daily pain and sleep interference from 0 ('none') to 10 ('pain as bad as you can imagine' or 'complete interference') every night. Baseline values were recorded for 7 days before starting study medication. The primary endpoint was change in mean of average daily pain scores from baseline to final week. Secondary efficacy outcomes included pain intensity, sleep interference, quality of life, mood, and global impression of change. Potential study limitations included permission to use serotonin reuptake inhibitors concomitantly (except venlafaxine or duloxetine) and the lack of a tramadol-alone or APAP-alone control group.
Results: A total of 160 subjects received tramadol/APAP and 153 received placebo. Tramadol/APAP reduced average daily pain significantly compared to placebo from baseline to the final week (-2.71 vs. -1.83, p = 0.001). Tramadol/APAP was associated with significantly greater improvement than placebo (p < or = 0.05) for all measures of pain intensity, sleep interference, and global impression, as well as several measures of quality of life and mood. The only adverse event reported by > 10% of subjects in either the tramadol/APAP or placebo group was nausea (11.9% and 3.3%, respectively). Adverse events resulted in early study discontinuation for 8.1% and 6.5% of subjects in the tramadol/APAP and placebo groups, respectively.
Conclusion: Tramadol/APAP was more effective than placebo and was well tolerated in the management of painful DPN.
Trial registration: ClinicalTrials.gov NCT00210847.