Oxaprozin versus diclofenac in NSAID-refractory periarthritis pain of the shoulder

Objective: To evaluate the efficacy and safety of oxaprozin in comparison with diclofenac in patients with periarthritis pain of the shoulder previously unsuccessfully treated with nonsteroidal anti-inflammatory drugs other than diclofenac and oxaprozin. Methods: In this open, multicentre, randomised, controlled study, eligible patients with periarthritis of the shoulder were randomised to receive either oxaprozin 1200 mg once daily (n = 49) or diclofenac 50 mg three times daily (n = 47). The treatment period was 15 ± 1 days. The study was planned on a hypothesis of equivalence between the two study drugs. The primary study endpoint was the change from baseline at day 15 in the patient-assessed shoulder pain score. Secondary efficacy variables included investigator-assessed shoulder function, patient-assessed quality of life on the Short-Form-36 (SF-36) Acute Health Survey and both patients' and investigators' overall assessment of efficacy. Results: At day 15, the mean changes in shoulder pain score from baseline in the oxaprozin and diclofenac groups were -5.85 ± SD 4.62 and -5.54 ± SD 4.41, respectively. The difference between the two groups was not statistically significant, confirming the hypothesis of the study that oxaprozin is as effective as diclofenac. Investigator-assessed shoulder function improved in both groups but more so in the oxaprozin group (p = 0.028 at day 15). Quality of life as measured by SF-36 total score was also improved in both treatment groups, with a trend toward greater improvement in the oxaprozin group. Furthermore, a significantly more favourable effect on the SF-36 'mental health' item was observed in oxaprozin compared with diclofenac-treated patients at day 15 (p = 0.0202). As assessed by investigators, the overall efficacy of oxaprozin was superior to that for diclofenac at visit 3 (8 ± 1 days) (p = 0.0067). Patients also assessed the overall efficacy of oxaprozin as superior to that of diclofenac at visits 3 (8 ± 1 days) (p = 0.0235) and 4 (15 ± 1 days) (p = 0.0272). Only six adverse events, all of which were mild or moderate in intensity and occurred in four diclofenac recipients, were observed in the study. Conclusions: As expected, once-daily oxaprozin proved to be as effective as diclofenac three times daily in reducing the primary efficacy variable of patient-assessed shoulder pain score in patients with periarthritis of the shoulder refractory to previous treatments with other NSAIDs. Oxaprozin was shown to be superior to diclofenac in improving shoulder function and was considered by investigators and patients to have greater overall efficacy than diclofenac. In addition, oxaprozin showed a trend toward superior results in improving patients' quality of life compared with diclofenac. A trend towards better tolerability results for oxaprozin compared with diclofenac was also noted.