Recurrent Pancytopenia Associated with Olanzapine Rechallenge: A Rare Case Report with Literature Review

Abstract Olanzapine is a frequently used second-generation antipsychotic, often considered to have a favorable hematological safety profile than clozapine. We report a rare case of recurrent pancytopenia associated with olanzapine rechallenge in a 46-year-old woman with acute psychotic episode. She had previously responded well to olanzapine but developed moderate hematological decline, which resolved on discontinuation. During current psychotic episode, olanzapine was re-initiated, and serial blood counts suggested progressive pancytopenia, which was confirmed on peripheral smear. Alternative causes including nutritional deficiencies and autoimmune disorders were ruled out. Olanzapine was discontinued and replaced with aripiprazole, following which all three cell lines normalized subsequently. This case demonstrates a clear temporal challenge–dechallenge–rechallenge association, confirming olanzapine as the causative agent. Clinicians should maintain a high degree of suspicion for hematological adverse effects even with olanzapine, especially in patients with prior cytopenic episodes. In such patients, baseline and serial hematological monitoring is advised and rechallenge is contraindicated.