Copper-salicylate gel for pain relief in osteoarthritis: A randomised controlled trial

Objective: To assess the efficacy and safety of a copper-salicylate gel in osteoarthritis of the hip and knee. Design: Randomised, double-blind, placebo-controlled study. Setting: Rheumatology Clinic of St Vincent's Hospital, Sydney, New South Wales (a tertiary referral hospital), June 1993 to October 1994. Patients: 116 patients with pain associated with osteoarthritis of the hip and/or knee (diagnosed by criteria of the European League against Rheumatism), drawn from patients attending the Clinic or self-referred after newspaper advertisements. Intervention: Copper-salicylate or placebo gel (1.5 g) applied twice daily to the forearm for four weeks. Outcome measures: Self-assessment of pain before the trial and after two and four weeks of treatment; patient and investigator assessments of efficacy; additional analgesia required; adverse reactions; and withdrawal rates. Results: Pain scores at rest and on movement decreased in both the copper-salicylate and placebo groups by 13%-20%. There was no significant difference between the two groups for decrease in pain score, patient and investigator efficacy ratings, number of patients requiring paracetamol for extra analgesia (active, 77%; placebo, 71%) and average dose of paracetamol (active, 555 mg/day; placebo, 600 mg/day). Significantly more patients in the copper-salicylate group reported adverse reactions (83% versus 52% of the placebo group), most commonly skin reactions, and withdrew from the trial because of these reactions (17% versus 1.7% of the placebo group). Conclusion: Copper-salicylate gel applied to the forearm was no better than placebo gel as pain relief for patients with osteoarthritis of the hip or knee, but produced significantly more skin rashes.