Seizure Associated with Olanzapine

OBJECTIVE: To report a case of seizures in a patient who started receiving olanzapine, and to review seizure risk associated with antipsychotic use. CASE SUMMARY: A 31-year-old African-American woman with multiple psychiatric and medical disorders, including generalized seizure disorder, experienced seizure activity when switched from haloperidol to olanzapine. Olanzapine was discontinued, haloperidol was quickly titrated to the previous dose, and the patient was started on oral phenytoin with no further seizure activity noted. The patient remained seizure free and phenytoin was discontinued without complications. DISCUSSION: Determining causality in this case is complicated by the number of confounding factors that may have contributed to the occurrence of seizures in this patient. These factors include: (1) diagnosis of generalized seizure disorder, (2) diagnosis of organic mental disorder, (3) concurrent pharmacotherapy with medications implicated in lowering the seizure threshold, and (4) abrupt change in pharmacotherapy. The likelihood that a significant drug interaction precipitated seizure activity is doubtful. CONCLUSIONS: Considering all factors related to causality, the likelihood that olanzapine was responsible for precipitating seizure activity in this patient was judged possible. Although premarketing studies have indicated that olanzapine may be associated with minimal seizure liability, this case serves as a reminder that postmarketing surveillance of newly released medications is essential.