Incidence of selective serotonin reuptake inhibitor (SSRI) induced hyponatraemia due to the syndrome of inappropriate antidiuretic hormone (SIADH) secretion in the elderly.

OBJECTIVE

The study determines the incidence of SSRI-induced hyponatraemia due to SIADH in an elderly psychiatric inpatient population.

DESIGN

A retrospective case-note study.

SETTING

An acute old age psychiatry ward.

SAMPLE

Patients admitted from January 1 to December 31, 1996.

MEASURES

Demographics, medication, psychiatric diagnoses, plasma sodium level and physical comorbidity were collected. Patients on SSRIs were selected and those developing hyponatraemia due to SIADH were identified.

RESULTS

Of 32 patients taking SSRIs, four developed symptomatic hyponatraemia due to SIADH (12.5%). A further four developed asymptomatic hyponatraemia following introduction of an SSRI (12.5%), although laboratory confirmation of SIADH was lacking.

CONCLUSIONS

The incidence of SSRI-induced hyponatraemia due to SIADH has not previously been established. This study shows a high incidence in elderly patients of this potentially dangerous complication. Clinical practice in the prescription of SSRIs to elderly people must change to include monitoring of electrolytes for early detection and reduction of morbidity.