Randomized double-blind study of cyclosporin in chronic 'idiopathic' urticaria.

BACKGROUND: Histamine-releasing activity (HRA) is detectable in up to 50% of patients with chronic ordinary urticaria.

OBJECTIVES: To determine the effect of cyclosporin on clinical features and HRA in patients with chronic urticaria.

METHODS: Thirty patients with severe unremitting disease, responding poorly to antihistamines and showing a positive autologous serum skin test (ASST) as a marker of HRA, were randomized to 4 mg kg-1 daily of cyclosporin (Sandimmun, n = 20) or placebo (n = 10) for 4 weeks. Non-responders were offered open-label cyclosporin for 4 weeks. All were followed for up to 20 weeks or until clinical relapse; all took cetirizine 20 mg daily throughout the study. The primary measure of efficacy was a daily urticaria activity score (UAS) of weal numbers and itch (maximum score 42 per week). A positive response was defined as a reduction to < 25% of baseline weekly UAS and relapse as a return to > 75%. The effect of cyclosporin on serum HRA was assessed by in vitro basophil histamine release assays and ASSTs before and after treatment.

RESULTS: Twenty-nine patients (19 active, 10 controls) completed the randomized trial medication. Eight of 19 on active treatment but none on placebo had responded at 4 weeks (P < 0.05). Three others on active drug met the criterion for response at 2 weeks but not at 4 weeks. Mean reduction in UAS between weeks 0 and 4 was 12.7 (95% confidence interval, CI 6.6-18.8) for active and 2.3 (95% CI - 3.3-7.9) for placebo (P = 0.005). Seventeen non-responders (seven randomized to active and 10 to placebo) chose open-label cyclosporin and 11 responded after 4 weeks. Six of the eight randomized active drug responders relapsed within 6 weeks. Of the 19 responders to randomized and open-label cyclosporin, five (26%) had not relapsed by the study end-point. Mean in vitro serum HRA fell from 36% (95% CI 22-49%) to 5% (95% CI 1-8%) after cyclosporin treatment (n = 11, P < 0.0001). The ASST response to post-treatment serum was also reduced (P < 0.05).

CONCLUSIONS: This study shows that cyclosporin is effective for chronic urticaria and provides further evidence for a role of histamine-releasing autoantibodies in the pathogenesis of this chronic 'idiopathic' disease.