Effects of Long-Term Treatment with Low Dose Cimetidine on Allergen-Induced Airway Responses and Selected Immunological Parameters in Atopic Asthmatics

ABSTRACT

Twenty asymptomatic atopic asthmatics were treated with either cimetidine 100 mg orally (13 patients) or placebo (7 patients) once a day for 4 weeks. Bronchial challenges were performed with the pertinent allergen immediately before and 2 and 4 weeks after the initiation of treatment and, finally, 4 weeks after the cessation of treatment. Before each challenge blood was drawn for the determination of specific IgE antibody levels (RAST procedure) and total IgE (PRIST), allergen- and anti-IgE-induced basophil histamine release, and mitogen-induced lymphocyte (³H)-thymidine incorporation. Patients treated with cimetidine were found to be significantly (P < 0.0.5) less responsive to bronchial allergen challenge during the treatment than before it; patients treated with placebo were more reactive (P < 0.05) 14 days after the initiation of treatment. The difference in responsiveness to treatment between the placebo and the cimetidine groups was significant 14 days (P < 0.01) and 4 weeks (P < 0.05) after the initiation of treatment; no significant difference in allergen responsiveness was recorded between the groups 1 month after cessation of treatment. No clear-cut changes in specific IgE antibody or total IgE levels, histamine release capacity, or mitogen-induced lymphocyte responsiveness were observed in either group, except that lymphocytes from cimetidine-treated patients tended to show an increased ratio of PHA- to PMA-induced thymidine incorporation. Thus, it was found that the treatment of asymptomatic atopic asthmatics with low-dose cimetidine reduced their allergen sensitivity in bronchial provocation tests by a mechanism which remains to be elucidated.