Rhabdomyolysis associated with clozapine treatment in a patient with decreased calcium-dependent potassium permeability of cell membranes.

A 21-year-old patient developed rhabdomyolysis during his nineteenth week of treatment with clozapine for drug-resistant schizophrenia. No risk factors for rhabdomyolysis were found, but the calcium-dependent potassium efflux, normally responsible for membrane hyperpolarization and muscle refractoriness, was severely decreased in the patient's red blood cells. Clozapine is speculated to cause rhabdomyolysis in patients with defective calcium-activated K+ channels.