Objective: To use the technique of meta-analysis to undertake a systematic review of published and unpublished randomized controlled trials of pharmacological agents to determine their relative efficacy and toxicity in the treatment of psoriatic arthritis.

Methods: Literature search using search terms of psoriasis, arthritis and controlled/randomised trial. The need for uniform data presentation necessitated correspondence with a number of original authors. The main outcome measure was the change in pooled disease index with component variables derived from OMERACT.

Results: Nineteen randomised trials were identified of which twelve were included in the quantitative analysis with data from 792 subjects. Although all agents were better than placebo, parenteral high dose methotrexate and salazopyrin were the only two agents that achieved statistical significance. In all trials the placebo group improved over baseline (pooled improvement 0.43 DI units, 95% CI 0.28-0.59). There was insufficient data to examine toxicity.

Discussion: Parenteral high dose methotrexate and salazopyrin are the only two agents with well demonstrated published efficacy in psoriatic arthritis. The magnitude of the effect seen with etretinate, oral low dose methotrexate, azathiaprine and perhaps colchicine suggests that they may be effective but that further multicentre clinical trials are required to establish their efficacy. Furthermore, the magnitude of the improvement observed in the placebo group strongly suggests that uncontrolled trials should not be used to guide management decisions in this condition.