Severe hyponatremia induced by the association of fluoxetine, hydrochlorothiazide andcaptopril in a young patient

Abstract

We describe a case of severe hyponatremia, with some of the lowest levels of sodium in the literature, secondary to the use of fluoxetine, captopril and hydrochlorothiazide. A 45-year-old female patient suffering from arterial hypertension who was being treated with hydrochlorothiazide and captopril was asymptomatic until one month prior to hospitalization when treatment with fluoxetine was initiated due to depressive symptoms. The patient was hospitalized due to a lower level of consciousness. A CT scan of the skull revealed cerebral edema and the biochemical analysis showed serum levels of sodium of 97 mEq/L. The patient presented favorable evolution after the discontinuation of the medication and with the use of 3% hypertonic saline. The mechanism through which drugs promote hyponatremia varies and is not fully understood. In the case of thiazide diuretics the alteration in sodium homeostasis and water in the renal tubes is the principal relation with this electrolyte disturbance. With antidepressants, however, the increased production of antidiuretic hormone is the most probable. ACE inhibitors are also related to hyponatremia, since bradykinin and angiotensin would stimulate the antidiuretic hormone. Therefore, the medical staff should perform the screening through a careful clinical assessment and tests of concentrations of serum levels of sodium in these patients in the early detection of potentially fatal electrolyte disturbances.