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

To assess the efficacy and safety of a copper-salicylate gel in osteoarthritis of the hip and knee.

Randomised, double-blind, placebo-controlled study.

Rheumatology Clinic of St Vincent's Hospital, Sydney, New South Wales (a tertiary referral hospital), June 1993 to October 1994.

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.

Copper-salicylate or placebo gel (1.5 g) applied twice daily to the forearm for four weeks.

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.

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).

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.