Cimetidine in systemic mastocytosis.

54-year-old caucasian women with systemic mastocytosis manifested by gastrointestinal and dermatological symptoms that were treated with cyproheptadine, Lomotil (diphenoxylate-atropine), and cimetidine was studied. The patient consented to discontinue the H2-receptor antagonist, and to have the following values measured: serum and urine concentrations of cimetidine: complete blood count (CBC) with differential, serum chemistry, and urinalysis; and systemic mastocytosis symptomatology. The patient experienced prompt recurrence of gastrointestinal and dermatological symptoms after stopping the cimetidine; the drug was restarted in three days and the symptoms subsided. The preceding laboratory and symptomatological values were recorded for 11 days after the reinstitution of cimetidine therapy. Histamine, gastrin, CBC, serum chemistry, and urinalysis remained normal, with and without cimetidine. Exacerbations of her symptoms were worst when no drug was detected in the serum. Therefore, it appears that cimetidine has a role in treating the symptoms of systemic mastocytosis.