Identifying causative medications for agranulocytosis: A case report of an older adult with cerebral infarction.

Key Clinical Message: Most drugs that cause adverse events are difficult to identify in critically ill patients undergoing polypharmacy. We share our experience in identifying the causative drug among four suspect drugs administered during emergency treatment.

Abstract: We present the case of a 93-year-old man who was admitted for the treatment of cerebrovascular events. The patient was initially prescribed dual antiplatelet therapy with aspirin and clopidogrel along with lansoprazole, Hange-koboku-toh, and elobixibat. On day 36 after admission, the patient was found to have developed agranulocytosis. To improve his cerebrovascular prognosis, we first discontinued medications other than the anticoagulant medicines and initiated filgrastim. We discontinued clopidogrel 9 days after the discontinuation of the other medicines considering his low white blood cell count. One day after the discontinuation of clopidogrel, the agranulocytosis was alleviated. Considering the time course, clopidogrel, lansoprazole, Hange-koboku-toh, and elobixibat were suspected as the culprit medicines. This case highlights the considerable challenges encountered in clinical practice when attempting to identify the drugs responsible for agranulocytosis, particularly in patients on intensive medication therapy.