HYPONATREMIA AND THE SYNDROME OF INAPPROPRIATE ANTIDIURETIC-HORMONE SECRETION ASSOCIATED WITH DRUG-THERAPY IN PSYCHIATRIC-PATIENTS

Hyponatraemia, the most common electrolyte disorder of all hospitalised patients, is particularly common in psychiatric patients. Hyponatraemia is generally defined as a serum sodium level of less than 135 mmol/L. Certain psychotropic medications may predispose to hyponatraemia; yet a causative role for mast has not been firmly established and their effect is most likely to be idiosyncratic. Certain factors such as age, schizophrenia and a history of hyponatraemia or polydipsia should alert the clinician to the need for closer follow-up. Although the majority of cases of hyponatraemia associated with psychotropic medications occur soon after initiation of the medication, some may occur much later. Thus, it is imperative to check a serum sodium level whenever patients who are receiving psychotropic medications have a marked change in their underlying disease, significant increases in bodyweight, seizures or other symptoms of hyponatraemia. Immediate treatment of hyponatraemia includes discontinuation of psychotropic drugs associated with hyponatraemia whenever possible, and treatment should be tailored to the underlying cause. Rapidity of correction should be determined by the chronicity of the hyponatraemia and whether the patient is symptomatic from the hyponatraemia. Strict adherence to guidelines for correction should be observed to prevent brain damage from pontine and extrapontine myelinolysis. Treatment of chronic hyponatraemia is best focused on the underlying psychiatric disorder. Overall, adherence to guidelines for early diagnosis and appropriate treatment of hyponatraemia will prevent mortality and reduce morbidity.