Hypertension, Thiazide, and Hyponatremia

Approximately three in 10 patients being treated for hypertension with thiazides develop hyponatremia, according to the results of a retrospective cohort study published recently in The American Journal of Medicine.

Researchers in the division of general internal medicine and primary care at Brigham and Women’s Hospital in Boston undertook the research to study the risk of thiazide-induced hyponatremia. Although hyponatremia is a well-recognized complication of treatment with thiazide diuretics, their effect remains unclear.

The clinicians conducted a retrospective cohort study using a multicenter clinical research registry. They identified 2,613 adult outpatients that were newly treated for hypertension from 2000 through 2005 at two teaching hospitals in Boston. The patients were followed for up to 10 years.

In the group exposed to thiazide, 66 (30%) developed hyponatremia (sodium ≤130 mmol/L). The adjusted incidence rate of hyponatremia was 140 cases per 1,000 person-years for patients treated with thiazides, compared with 87 cases per 1,000 person-years in those without thiazides.

“Patients exposed to thiazides were more likely to develop hyponatremia (adjusted incidence rate ratio, 1.61; 95% confidence interval [CI], 1.15-2.25),” the authors wrote in the study abstract. “There was no significant difference in the risk of hospitalizations associated with hyponatremia (adjusted rate ratio, 1.04; 95% CI, 0.46-2.32) or mortality (adjusted rate ratio, 0.41; 95% CI, 0.12-1.42). The number needed to harm (to result in one excess case of incident hyponatremia in 5 years) was 15.02 (95% CI, 7.88-160.30).”

SourceRisk of Thiazide-induced Hyponatremia in Patients with Hypertension [The American Journal of Medicine]