Generalised tonic-clonic seizures on the subtherapeutic dose of olanzapine

Area of Science:

• Neuroscience
• Psychopharmacology
• Clinical Neurology

Background:

• Olanzapine, a second-generation antipsychotic, is generally associated with a low incidence of seizures when used as monotherapy.
• Risk factors for olanzapine-induced seizures (OIS) include combination antipsychotic therapy, impaired drug metabolism, and advanced age.

Observation:

• A 71-year-old male patient with bipolar affective disorder, depression, and dementia was treated with a subtherapeutic dose of olanzapine (1.25 mg twice daily).
• Within 24 hours of initiating olanzapine, the patient experienced a generalized tonic-clonic seizure lasting approximately two and a half minutes.
• Electroencephalogram (EEG) revealed mild slowing, suggestive of a potential impact on brain activity.

Findings:

• This case report documents olanzapine-induced seizures (OIS) occurring at a subtherapeutic dosage, challenging the assumption that seizures are primarily linked to therapeutic ranges.
• The patient presented with multiple established risk factors for OIS, including advanced age, cognitive impairment, a history of stroke, and a prior post-stroke seizure.

Implications:

• Physicians may underestimate the risk of OIS at subtherapeutic doses due to the scarcity of evidence, particularly in patients with co-existing risk factors.
• This case underscores the importance of vigilant seizure risk assessment in elderly patients with cognitive impairment initiating olanzapine, even at reduced dosages.
• Further research is warranted to elucidate the precise mechanisms and dose-dependent seizure threshold of olanzapine in vulnerable patient populations.