In a new study, researchers found that chlorthalidone, the guideline-recommended diuretic for lowering blood pressure, causes more serious side effects than hydrochlorothiazide, a similarly effective diuretic.
The findings contrast with current treatment guidelines recommending chlorthalidone over hydrochlorothiazide.
The research was led by a team at Columbia University Irving Medical Center.
In the study, the team looked at 17 years of data on more than 730,000 people treated for high blood pressure.
They found that chlorthalidone and hydrochlorothiazide were similarly effective in preventing a heart attack, hospitalization for heart failure, and stroke.
However, patients taking chlorthalidone had nearly three times the risk of developing dangerously low levels of potassium and a greater risk of other electrolyte imbalances and kidney problems compared with those taking hydrochlorothiazide.
The side effects can lead to abnormal heart rhythms; hyponatremia (low sodium), which can cause confusion, kidney failure, and type 2 diabetes.
They found that 6.3% of patients treated with chlorthalidone experienced hypokalemia (low blood potassium), compared with 1.9% of patients who were treated with hydrochlorothiazide.
Hypokalemia rates remained higher for patients taking chlorthalidone even when given at a lower dose than hydrochlorothiazide.
The team says doctors prescribing chlorthalidone should monitor for certain side effects in their patients.
The new study is not the first to find side effects associated with chlorthalidone.
A previous observational study found that the drug was linked to more electrolyte imbalances than hydrochlorothiazide.
The lead author of the study is George Hripcsak, MD, MS, chair and Vivian Beaumont Allen Professor of Biomedical Informatics.
The study is published in JAMA Internal Medicine.
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