[Olanzapine induced rhabdomyolysis and serum creatine kinase increase]

"Atypical" antipsychotics tend to replace traditional antipsychotics as first line therapy for psychotic disorders, due to their better side-effect profile with fewer extrapyramidal manifestations, allowing a better observance. Nevertheless, second-generation antipsychotics may also lead to adverse events such as metabolic disorders, agranulocytosis or muscle damage. Cases of rhabdomyolysis (aside neuroleptic malignant syndrome) have been reported in patients receiving olanzapine (Zyprexa).

We reviewed the cases of olanzapine induced rhabdomyolysis reported to the French national database of drug adverse events and retrieved additional cases published in the medical literature.

We collected 13 cases from the French pharmacovigilance database and eight additional cases from the literature. Seventeen patients needed hospitalization. Creatine kinase (CK) rate ranged between 413 and 34,500 UI/L. Outcome was favorable in 85% of the cases (17 out of 20 cases) after discontinuation of olanzapine.

Although rhabdomyolysis is a rare side effect (< 1%) of olanzapine, this adverse event should be evoked when a patient with olanzapine presents with muscle pain, unexplained fatigue or weakness. Prompt dosage of CK should be performed. However, it remains uncertain whether a mild and asymptomatic muscle enzyme increase without any metabolic disorder requires the discontinuation of olanzapine therapy.