Low salt intake and changes in serum sodium levels in the combination therapy of low-dose hydrochlorothiazide and angiotensin II receptor blocker

Abstract

Background: Although a low salt intake and angiotensin II blockade may act to reduce serum sodium (srNa) levels during low-dose diuretic treatment, the effects of these factors on srNa level have not yet been fully clarified. The present study was conducted to examine the association of dietary salt intake with the changes in srNa levels when angiotensin II receptor blocker (ARB) treatment is changed to the combination of ARB plus a low-dose diuretic, Hydrochlorothiazide (HCTZ). Methods: In 88 patients (age 70±12 years old), ARB treatment was switched to the combination drug (the same dosage ARB plus 12.5 mg/day HCTZ). srNa level was measured before and 6 months after administration of this combination drug. The daily salt intake was estimated by the Kawasaki formula using second morning urine. Results: The study subjects were divided into quintile ranges according to the daily salt intake. The reduction in srNa levels by switching to the ARB plus HCTZ treatment was significant in subjects in the lowest quintile Q5 (7.22 g/day or less salt intake), but not in those in Q1-4 (17.78-7.25 g/day salt intake). Increases in serum creatinine and uric acid levels, however, were significantly larger in the former group than in the latter group. ![Figure][1] Conclusions: In the strict low salt intake condition (< 7.2 g/day), the addition of a low-dose diuretic (12.5 mg HCTZ) to ARB treatment causes significant reductions in srNa levels, which might affect blood osmolarity. [1]: pending:yes