Cimetidine does not impair lung host defense in experimental pneumococcal pneumonia.

Normal CD-1 mice were administered cimetidine (400 mg/kg/24 h) or control solution by subcutaneous injection and inoculated intratracheally with type S Streptococcus pneumoniae in order to evaluate the effect of the histamine H2-receptor antagonist on pulmonary antibacterial mechanisms. Therapy with cimetidine did not influence overall survival rates. After challenge with 1 X 10(6) colony-forming units (cfu), the eradication of viable pneumococci from the lungs (pulmonary clearance), the generation of a local inflammatory response, and the prevalence of bacteremia were similar in both study groups. Cimetidine also failed to influence pulmonary antimicrobial systems after challenge with lower bacterial inocula (5 X 10(4) and 5 X 10(3) cfu). Further, treatment with cimetidine had no effect on the in vivo phagocytic or bactericidal activity of resident murine alveolar macrophages. Thus, in this animal model, cimetidine does not disrupt host defenses of the lower respiratory tract.