The addition of piroxicam to topically applied glyceryl trinitrate enhances its analgesic effect in musculoskeletal pain: a randomised, double-blind, placebo-controlled study

Objective: To investigate the analgesic effect of topically applied 1% glyceryl trinitrate (GTN), 2.5% piroxicam and a mixture containing 2.5% piroxicam with 1% GTN in patients with chronic musculoskeletal pain. Methods: A randomised, double-blind, placebo-controlled study of 200 patients with musculoskeletal pain of at least 3 months. Patients were randomly assigned in equal numbers to one of four treatment groups: placebo, 1% GTN, 2.5% piroxicam, and 2.5% piroxicam/1% GTN and they applied it topically over the painful area for 4 weeks. Results: 157 of 200 patients completed the study. Baseline visual analogue pain score was 6.23. After 4 weeks there was a significant reduction in pain scores in the piroxicam/GTN (to 5.48, 95% confidence limits 4.63-6.33) with no fall in the placebo or piroxicam groups. Pain score fell by week 3 in the GTN group, but reverted to baseline levels by week 4. Concomitant analgesic consumption was unchanged in the placebo and piroxicam groups, fell with piroxicam/GTN and increased with GTN use. Conclusion: Topical application of 2.5% piroxicam has no analgesic effects in musculoskeletal pain. However, topical application of 1% GTN has an analgesic effect (although tachyphylaxis develops) and this analgesic effect is magnified by the addition of 2.5% piroxicam to GTN.