Marked Elevation of Serum Creatine Kinase Associated with Olanzapine Therapy

OBJECTIVE: To report a case of marked elevation of serum creatine kinase (CK) associated with olanzapine therapy. CASE SUMMARY: A 39-year-old white Jewish schizophrenic man treated with olanzapine developed an elevated serum CK concentration with a peak concentration of 4000 IU/L (normal <230). No other diagnostic criteria for neuroleptic malignant syndrome (NMS) were present. On discontinuation of the drug, serum CK concentrations returned to normal within eight days. DISCUSSION: Olanzapine, like other atypical antipsychotic drugs, may cause muscle injury with concomitant elevations of serum CK of muscle origin. We suggest that in patients treated with olanzapine, CK concentrations should be checked on initiation of therapy, within the first 48 hours, and weekly thereafter for at least one month. In addition, patients with clinical signs suggestive of NMS should be monitored more carefully. For those patients with a history of NMS, or even of isolated serum CK elevation during antipsychotic therapy, follow-up should be stricter. CONCLUSIONS: Marked elevation of serum CK may be a possible complication of olanzapine therapy.