Cimetidine and hematologic suppression: things are not always as they appear

Area of Science:

• Hematology
• Pharmacology
• Gastroenterology

Background:

• Cimetidine is a histamine H2 receptor antagonist used to treat acid-related gastrointestinal disorders.
• Hematologic suppression, including neutropenia and thrombocytopenia, has been rarely reported with cimetidine use.
• Bone marrow suppression can have multifactorial causes, complicating drug causality assessment.

Observation:

• A 67-year-old male with a bleeding ulcer developed fever, thrombocytopenia, and neutropenia with eosinophilia during cimetidine therapy (3600 mg/day).
• Hematologic parameters normalized after discontinuation of cimetidine.
• Subsequent rechallenge with cimetidine did not result in recurrence of the hematologic suppression.

Findings:

• The patient's presentation mimicked previously reported cases of cimetidine-associated hematologic suppression.
• The lack of reproducibility upon rechallenge makes definitive attribution of hematologic changes to cimetidine challenging.
• The possibility of an idiosyncratic reaction to cimetidine causing bone marrow suppression is considered.

Implications:

• While rare, cimetidine-induced bone marrow suppression, potentially via idiosyncratic reactions, warrants consideration.
• Fatal outcomes like aplastic anemia are extremely rare, and the benefit-risk ratio should guide cimetidine rechallenge decisions.
• Further investigation into the mechanisms of cimetidine-induced hematologic effects is needed.