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Rhabdomyolysis After Correction of Hyponatremia in Psychogenic Polydipsia Possibly Complicated by Ziprasidone

¹ Chief Resident and Clinical Instructor, Department of Internal Medicine, The Pennsylvania State University, The Penn State Milton S Hershey Medical Center, 500 University Dr., Hershey, PA 17033-2360, fax 717/531-5831, azaidi{at}psu.edu

Reprints: Dr. Zaidi

OBJECTIVE: To report a case of rhabdomyolysis related to correction of hyponatremia secondary to psychogenic polydipsia, possibly complicated by the use of ziprasidone.

CASE SUMMARY: A 50-year-old white man treated for 3 weeks with ziprasidone 40 mg twice daily for chronic paranoid schizophrenia was admitted to the intensive care unit after a witnessed generalized seizure. Marked hypotonic hyponatremia was present secondary to psychogenic polydipsia. After correction of hyponatremia with intravenous NaCl 0.9%, he developed a substantial elevation in the creatine kinase level without any evidence of muscle trauma, stiffness, or swelling or any signs of neuroleptic malignant syndrome. Renal failure or compartment syndrome did not complicate the clinical picture.

DISCUSSION: It is well known that severe hyponatremia can cause neurologic complications such as stupor, seizures, and even coma. Hyponatremia from water intoxication (n = 28) and its correction with intravenous fluids (n = 2) may cause non-neurologic complications such as rhabdomyolysis. An explanation may lie within the calcium-sodium exchange mechanism across the skeletal myocyte or the failure of cell volume regulation secondary to extracellular hypo-osmolality. Neuroleptic medications have been linked to the development of rhabdomyolysis, with antipsychotics being the primary offenders. As of August 2005, there has been only one reported case of rhabdomyolysis related to correction of hyponatremia complicated by an atypical antipsychotic (clozapine). It is possible that ziprasidone, like clozapine, may enhance muscle cell permeability leading to rhabdomyolysis under similar conditions.

CONCLUSIONS: Psychiatric patients treated with atypical antipsychotic medications should be closely monitored for rhabdomyolysis during correction of hyponatremia, thus permitting prompt therapy to limit its complications.

Key Words: psychogenic polydipsia, schizophrenia, ziprasidone

Published Online, August 30, 2005. www.theannals.com, DOI 10.1345/aph.1E518