H2 blockers in chronic urticaria.

Two hundred unselected patients with chronic idiopathic urticaria were treated with adequate doses of conventional antihistamines given at frequent intervals; 98.5% were completely freed of disease while on therapy. In three cases, the lesions subsided but did not clear completely. The addition of 800 mg of cimetidine in divided doses cleared the lesions in two cases, and in the third case the dose of H1 blocker was increased, which resulted in complete clearance of wheals and symptoms. Addition of H2 blockers play a role, but only in a very small percentage of patients with chronic idiopathic urticaria who do not completely respond to adequate doses of H1 blockers.