Olanzapine-Induced Rhabdomyolysis and Hyponatremia: A Case Report

Olanzapine, a second-generation antipsychotic, is generally well tolerated but can rarely be associated with serious complications such as rhabdomyolysis and hyponatremia. We report the case of a woman in her early forties with a 15-year history of paranoid schizophrenia who developed bilateral foot drop and seizures in the context of severe hyponatremia and markedly elevated creatine phosphokinase (CPK) levels. Symptoms arose after olanzapine dose escalation from 10 to 20 mg daily to address difficult psychiatric symptoms. Magnetic resonance imaging (MRI) showed diffuse T2 hyperintensity in calf muscles, and nerve conduction studies revealed bilateral common peroneal neurapraxia. The presentation was attributed to olanzapine-induced syndrome of inappropriate antidiuretic hormone secretion (SIADH) and rhabdomyolysis. Both olanzapine and Lurasidone were stopped on admission; sequential re-challenge identified olanzapine as the probable causative agent. This case highlights the importance of early recognition of muscle symptoms and electrolyte disturbances in patients on antipsychotics, particularly following dose adjustments.