(P-IG-22) First Reported Case of Famotidine-induced Immune Hemolytic Anemia

Background/Case Studies: Drug-induced immune hemolytic anemia (DIIHA) is a rare phenomenon that may result in life-threatening complications. We report a case of DIIHA caused by antibodies directed to famotidine (Pepcid®). Famotidine has not been previously reported to be implicated in cases of DIIHA.

Study

Design/Methods: A 43-year-old female being treated for breast cancer was receiving intravenous (IV) famotidine as a prophylactic for IV chemotherapy. It was reported to our lab that during one of her treatments, she began experiencing a burning sensation with pain near the infusion site in the upper left chest, pain in both upper and lower extremities, nausea, chills, rigor, red swollen feet, and red urine. Following the adverse event, visual hemolysis was observed in the patient’s plasma as well as a positive direct antiglobulin test (DAT). DIIHA was suspected and samples from the patient, collected four days post-infusion, along with a supply of IV famotidine was referred to our facility for a drug-dependent RBC antibody study.

Serologic testing was done by standard tube methods using reagent red cells prepared in-house, antihuman globulin reagents (Ortho-Clinical Diagnostics, Immucor), and acid eluate kit (Immucor).

Results/Findings: Initial reference lab testing on the sample drawn four days post-infusion showed the patient had a weakly reactive DAT with micro+ IgG and 2+ C3. Routine testing of the eluate was non-reactive with all cells tested. No alloantibodies were detected in a saline indirect antiglobulin test (IAT) or with ficin-treated red cells. Following routine testing, the patient’s serum was titrated and tested in both the presence of drug (IPOD) in 1 mg/mL concentration and against drug-treated red cells (DTRC).

With the addition of IV famotidine, patient’s serum showed positive reactivity with reagent red cells at all phases. There was complete hemolysis after a 37C incubation; however, use of pure famotidine resulted in visualization of both macro- and microscopic agglutination. Prozone effect was observed with DTRC. The patient’s eluate and a normal serum control was non-reactive when tested by IPOD and with DTRC. Serological results are summarized in Table 1.

Conclusions: These serological findings confirm the presence of famotidine-dependent antibodies causing hemolysis. This is the first reported case of famotidine-induced immune hemolytic anemia.

Importance of research: Famotidine has not been previously reported to be implicated in cases of DIIHA. This is the first reported case of famotidine-induced immune hemolytic anemia.