Pharmacogenetics Newsletter

Volume 3, Issue 15, 04/19/2011

Question

What genetic polymorphism has been associated with the risk of developing polydipsia induced hyponatremia in patients with schizophrenia taking risperidone (Risperdal)?

Answer

Polydipsia is considered either a chronic or intermittent ingestion of large volumes of water, which results in a dilution of blood components such as sodium.  It has been estimated that approximately 20% of psychiatric inpatients (mainly schizophrenic patients) will experience polydipsia with at least 5% of those experiencing water intoxication at some point in their lifetime.(1)  If severe enough, polydipsia induced hyponatremia can cause a number of disturbances in the central nervous system (CNS) which include delirium, ataxia, seizures and death. 

Interestingly, the use of antipsychotics in the management of schizophrenia has been associated with causing this condition.  Of the antipsychotics involved, the...

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