RESUMEN
BACKGROUND: Clozapine is a highly effective second-generation antipsychotic with few extrapyramidal reactions, making it a preferred choice among clinicians. However, instances of acute clozapine poisoning resulting from suicide attempts and misuse have been reported. Through our review of existing literature, we identified that we believe to be the highest recorded overdose of clozapine in elderly patients, resulting in a nonfatal outcome. CASE PRESENTATION: The case report involves a 71-year-old female with a history of depression who ingested a dose of 10,000 mg of clozapine. Approximately 6 h after the overdose, the clozapine level was 5,200 µg/L, significantly surpassing the recommended therapeutic concentration range of 350-600 µg/L. After gastric lavage and hemoperfusion, the blood level dropped to 1847.11 µg/L. Notably, during therapeutic drugs monitoring (TDM), we found a perplexing spike in the patient's blood level to 5554.15 µg/L after the second hemoperfusion. CONCLUSION: In this case we mainly focused on the abnormal fluctuations in the concentration of clozapine. We conducted a comprehensive analysis of potential factors contributing to this abnormal phenomenon in terms of the patient's age, clinical symptoms, various laboratory test indexes, and the pharmacokinetics of clozapine. Our findings underscore the importance of timely TDM and the precision of results in managing elderly patients experiencing high-dose clozapine poisoning.