Investigation of the effects of a new transdermal formulation of systemic diclofenac on the upper gastrointestinal mucosa in patients with low back pain: A comparative study with oral diclofenac.

Background and aim: Non-steroidal anti-inflammatory drugs (NSAIDs) are associated with gastrointestinal mucosal damage attributed to a topical effect of NSAIDs on the gastrointestinal mucosa after oral administration and cyclooxygenase-1 inhibition. Diclofenac sodium systemic patch (DSSP), a transdermal patch from which diclofenac sodium is absorbed through the skin to exert its effects through the circulating blood, is considered to reduce the occurrence of gastrointestinal mucosal damage compared with oral diclofenac. This study aimed to compare the effect of DSSP on the upper gastrointestinal mucosa with that of an orally administered diclofenac sodium tablet (DST).

Methods: This randomized, evaluator-blinded study included Japanese patients with low back pain (LBP). The patients were administered with either DSSP (150 mg/day) or DST (75 mg/day) for 2 weeks. The primary endpoint was the incidence of gastroduodenal ulcers and/or erosions on upper gastrointestinal endoscopy after the study treatment.

Results: Thirty patients each were randomly assigned to the DSSP and DST groups. The incidence of gastroduodenal ulcers and/or erosions was 26.7% and 86.2% in the DSSP and DST groups, respectively. The difference in the incidence was -59.5% (95% confidence interval: -77.0 to -34.6). No adverse events (AEs) were observed in the DSSP group, and 20.0% (6/30 patients) reported mild AEs in the DST group (excluding ulcers and erosions).

Conclusion: DSSP is associated with a lower risk of gastrointestinal mucosal damage than DST, which has the same active ingredient but uses a different route of administration, in patients with LBP.