Case Report: Oral Cimetidine Administration Causes Drug-Induced Immune Hemolytic Anemia by Eliciting the Production of Cimetidine-Dependent Antibodies and Drug-Independent Non-specific Antibodies

Previously, it was reported that multiple patients had hemolytic anemia associated with cimetidine administration, while only one patient who had received intravenous cimetidine was serologically diagnosed with drug-induced immune hemolytic anemia (DIIHA) caused by cimetidine-dependent antibodies. However, the ability of oral cimetidine intake to induce the production of antibodies has not been examined. In this study, we report a 44-year-old male patient in whom oral cimetidine administration resulted in cimetidine-dependent antibodies and drug-independent non-specific antibodies, leading to the development of DIIHA. Serological tests showed that the results of DAT for anti-IgG (3+) and anti-C3d (1+) were positive. The IgM and IgG cimetidine-dependent antibodies (the highest total titer reached 4096) were detected in the plasma incubated with O-type RBCs and 1 mg/mL cimetidine or the plasma incubated with cimetidine-coated RBCs. IgG-type drug-independent non-specific antibodies were detected in blood samples collected at days 13, 34, 41, and 82 post-drug intake. This is the first study to report that the oral administration of cimetidine can elicit the production of cimetidine-dependent antibodies which promote DIIHA, and also elicit the production of drug-independent non-specific antibodies which causes hemolytic anemia that does not depend on cimetidine and lasts longer.