There was no difference in major cardiovascular outcomes with the use of two different diuretics – chlorthalidone or hydrochlorothiazide – in the treatment of hypertension in a new large randomized real-world study.
The Diuretic Comparison Project (DCP), which was conducted in more than 13,500 U.S. veterans age 65 years or over, showed almost identical rates of the primary composite endpoint, including myocardial infarction (MI), stroke, noncancer death, hospitalization for acute heart failure, or urgent revascularization, after a median of 2.4 years of follow-up.
There was no difference in any of the individual endpoints or other secondary cardiovascular outcomes.
However, in the subgroup of patients who had a history of MI or stroke (who made up about 10% of the study population), there was a significant reduction in the primary endpoint with chlorthalidone, whereas those without a history of MI or stroke appeared to have an increased risk for primary outcome events while receiving chlorthalidone compared with those receiving hydrochlorothiazide.
The DCP trial was presented at the American Heart Association scientific sessions by Areef Ishani, MD, director of the Minneapolis Primary Care and Specialty Care Integrated Care Community and director of the Veterans Affairs (VA) Midwest Health Care Network.
Asked how to interpret the result for clinical practice, Dr. Ishani said, “I think we can now say that either of these two drugs is appropriate to use for the treatment of hypertension.”
But he added that the decision on what to do with the subgroup of patients with previous MI or stroke was more “challenging.”
“We saw a highly significant benefit in this subgroup, but this was in the context of an overall negative trial,” he noted. “I think this is a discussion with the patients on how they want to hedge their bets. Because these two drugs are so similar, if they wanted to take one or the other because of this subgroup result I think that is a conversation to have, but I think we now need to conduct another trial specifically in this subgroup of patients to see if chlorthalidone really is of benefit in that group.”
Dr. Ishani explained that both chlorthalidone and hydrochlorothiazide have been around for more than 50 years and are considered first-line treatments for hypertension. Early studies suggested better cardiovascular outcomes and 24-hour blood pressure control with chlorthalidone, but recent observational studies have not shown more benefit with chlorthalidone. These studies have suggested that chlorthalidone may be associated with an increase in adverse events, such as hypokalemia, acute kidney injury, and chronic kidney disease.
Pragmatic study
The DCP trial was conducted to try to definitively answer this question of whether chlorthalidone is superior to hydrochlorothiazide. The pragmatic study had a “point-of-care” design that allowed participants and health care professionals to know which medication was being prescribed and to administer the medication in a real-world setting.
“Patients can continue with their normal care with their usual care team because we integrated this trial into primary care clinics,” Dr. Ishani said. “We followed participant results using their electronic health record. This study was nonintrusive, cost-effective, and inexpensive. Plus, we were able to recruit a large rural population, which is unusual for large, randomized trials, where we usually rely on big academic medical centers.”
Using VA electronic medical records, the investigators recruited primary care physicians who identified patients older than age 65 years who were receiving hydrochlorothiazide (25 mg or 50 mg) for hypertension. These patients (97% of whom were male) were then randomly assigned to continue receiving hydrochlorothiazide or to switch to an equivalent dose of chlorthalidone. Patients were followed through the electronic medical record as well as Medicare claims and the National Death Index.
Results after a median follow-up of 2.4 years showed no difference in blood pressure control between the two groups.
In terms of clinical events, the primary composite outcome of MI, stroke, noncancer death, hospitalization for acute heart failure, or urgent revascularization occurred in 10.4% of the chlorthalidone group and in 10.0% of the hydrochlorothiazide group (hazard ratio [HR], 1.04; 95% confidence interval [CI], 0.94-1.16; P = .4).
There was no difference in any individual components of the primary endpoint or the secondary outcomes of all-cause mortality, any revascularization, or erectile dysfunction.
In terms of adverse events, chlorthalidone was associated with an increase in hypokalemia (6% vs. 4.4%; HR, 1.38), but there was no difference in hospitalization for acute kidney injury.