Cimetidine and chlorpheniramine in the treatment of chronic idiopathic urticaria: a multi-centre randomized double-blind study.

One hundred and twenty patients with chronic idiopathic urticaria, who entered a study at five centres (Sheffield, London, Bristol, Cardiff and Leeds) were treated with therapeutic doses of the H1 antagonist chlorpheniramine for 6 weeks. Histamine H1 non-responders (40 patients) were entered into a double-blind study and received chlorpheniramine plus cimetidine 400 mg q.d.s. (21 patients) or chlorpheniramine plus placebo (19 patients) for a further 8 weeks. The most important response measure was the change from baseline of the total symptom score: an assessment of the number and duration of new weals and degree of itching. There was a statistically significant difference between the average response in the two treatment groups in favour of chlorpheniramine plus cimetidine after 4 and 8 weeks' treatment (P less than 0.05 and P less than 0.01, respectively). No significant side-effects related to treatment were noted.