Diuretic Comparison Project (DCP)
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The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. |
ClinicalTrials.gov Identifier: NCT02185417 |
Recruitment Status :
Completed
First Posted : July 9, 2014
Last Update Posted : January 19, 2023
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Condition or disease | Intervention/treatment | Phase |
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Hypertension | Drug: Hydrochlorothiazide (HCTZ) Drug: Chlorthalidone | Phase 3 |
Over 1 million Veterans are prescribed a thiazide-type diuretic each year; over 95% receive hydrochlorothiazide, and fewer than 2.5% receive chlorthalidone. Both medications are thiazide-type diuretics that have been used for more than 50 years and are considered first-line treatment for hypertension. Indirect evidence has been accumulating, however, that chlorthalidone may be more effective than hydrochlorothiazide at preventing cardiovascular events. This will be the first randomized head-to-head comparison of the effectiveness of these two drugs. The study plans to enroll 13,500 Veterans over 3 years and follow them on average for 3 years, resulting in a total study duration of 4.5 years. Patients currently prescribed hydrochlorothiazide will be randomized to either continue taking hydrochlorothiazide or to receive an equivalent dose of chlorthalidone. The unique 'point of care' or 'clinically integrated' study design will identify, enroll and follow subjects using the electronic medical record system and national VA and non-VA databases. The primary outcome is an event composite consisting of: stroke, myocardial infarction, non-cancer death, urgent revascularization, and hospitalization for acute congestive heart failure. All patient care, including the study drug, will continue to be managed by the primary care provider.
Primary Care Providers will also be included as participants in this research study. Adding providers as subjects will allow us to study the implementation of the point of care protocol design in addition to the original research question. The study team will collect data on diuretic management within the study and may contact providers by phone or email to learn reasons for declining a particular patient or discontinuing a new chlorthalidone order or an ongoing diuretic prescription.
If cardiovascular events are reduced by even a small amount by chlorthalidone, the public health effect will be considerable because of the large number of patients who take diuretics. A randomized trial, now feasible due to the investigators' efficient and inexpensive design, will provide evidence needed to better inform practice throughout the VA.
Study Type : | Interventional (Clinical Trial) |
Actual Enrollment : | 13523 participants |
Allocation: | Randomized |
Intervention Model: | Parallel Assignment |
Masking: | None (Open Label) |
Primary Purpose: | Treatment |
Official Title: | CSP #597 - Diuretic Comparison Project |
Actual Study Start Date : | June 15, 2016 |
Actual Primary Completion Date : | October 15, 2022 |
Actual Study Completion Date : | December 29, 2022 |

Arm | Intervention/treatment |
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Active Comparator: Hydrochlorothiazide
Hydrochlorothiazide daily dose of 50 mg or 25 mg for duration of study
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Drug: Hydrochlorothiazide (HCTZ)
Thiazide-type diuretic. Daily dose of 50 or 25 mg for duration of the study.
Other Name: HCTZ |
Active Comparator: Chlorthalidone
Chlorthalidone daily dose of 25 mg or 12.5 mg for duration of study
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Drug: Chlorthalidone
Thiazide-type diuretic. Daily dose of 25 or 12.5 mg for duration of the study. |
- Time to major cardiovascular event [ Time Frame: Randomization to time to event; average follow-up 3 years ]The Primary outcome measure will be time to a major cardiovascular event, defined as a composite outcome comprised of the first occurrence after randomization of any of the following: stroke, myocardial infarction, urgent coronary revascularization because of unstable angina, hospitalization for acute congestive heart failure, non-cancer death.
- Time to event for each component of the composite primary outcome and additional cardiovascular events [ Time Frame: Randomization to time to event; average follow-up 3 years ]The Secondary outcomes will include time to event for (1) each of the 5 components of the composite primary outcome, (2) all deaths, (3) the composite outcome substituting all deaths for non-cancer deaths, (4) "possibly vascular deaths," (5) the composite outcome substituting "possibly vascular deaths" for non-cancer deaths, (6) any revascularization of any artery.
- All Deaths [ Time Frame: Randomization to time to event; average follow-up 3 years ]All Deaths
- The primary composite outcome substituting 'all deaths' for 'non-cancer deaths' [ Time Frame: Randomization to time to event; average follow-up 3 years ]This secondary outcome measure will be time to a major cardiovascular event, defined as a composite outcome comprised of the first occurrence after randomization of any of the following: stroke, myocardial infarction, urgent coronary revascularization because of unstable angina, hospitalization for acute congestive heart failure, all deaths.
- Possibly Vascular Deaths [ Time Frame: Randomization to time to event; average follow-up 3 years ]Defined as all deaths caused by vascular diseases, diabetes, external causes, and unknown causes.
- The primary composite outcome substituting 'possibly vascular deaths' for 'non-cancer deaths' [ Time Frame: Randomization to time to event; average follow-up 3 years ]This secondary outcome measure will be time to a major cardiovascular event, defined as a composite outcome comprised of the first occurrence after randomization of any of the following: stroke, myocardial infarction, urgent coronary revascularization because of unstable angina, hospitalization for acute congestive heart failure, possibly vascular deaths. 'Possibly vascular deaths' are defined as all deaths caused by vascular diseases, diabetes, external causes, and unknown causes.
- Any revascularization of any artery [ Time Frame: Randomization to time to event; average follow-up 3 years ]Any revascularization of any artery
- Erectile dysfunction (ED) [ Time Frame: Randomization to time to event; average follow-up 3 years ]Defined as first prescription for phosphodiesterase Type 5 (PDE5) inhibitor or referral for ED

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Ages Eligible for Study: | 65 Years and older (Older Adult) |
Sexes Eligible for Study: | All |
Accepts Healthy Volunteers: | No |
Inclusion Criteria:
Veterans who:
- Are over age 65 years
- Are receiving hydrochlorothiazide from the VA pharmacy at a daily dose of 25 or 50 mg
- Have a most recent systolic blood pressure (SBP) in CPRS greater than or equal to 120 mm Hg, with no SBP less than 120 mm Hg recorded in CPRS in the previous 90 days
Primary Care Providers will also be included as participants in this research study.
Exclusion Criteria:
- Impaired decision-making capacity rendering the patient unable to provide informed consent (i.e., if there is any question during the nurse's EMR chart review that the individual does not have the ability to make an autonomous decision or the PCP declines permission to randomize)
- Death expected within 6 months (inferred by PCP permission to randomize)
- K<3.1 meq/L (or K<3.5 meq/L if on digoxin) in the past 90 days
- Na<130 meq/L in the past 90 days
- Known to be enrolled in Medicare Part C (assessed on consent phone call). This exclusion will only be employed if the investigators determine that sufficient information from Part C data cannot obtained.

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.
Please refer to this study by its ClinicalTrials.gov identifier (NCT number): NCT02185417

Study Chair: | Areef Ishani, MD MS | Minneapolis VA Health Care System, Minneapolis, MN | |
Study Chair: | William C Cushman, MD | Memphis VA Medical Center, Memphis, TN |
Other Publications:
Responsible Party: | VA Office of Research and Development |
ClinicalTrials.gov Identifier: | NCT02185417 |
Other Study ID Numbers: |
597 |
First Posted: | July 9, 2014 Key Record Dates |
Last Update Posted: | January 19, 2023 |
Last Verified: | January 2023 |
Individual Participant Data (IPD) Sharing Statement: | |
Plan to Share IPD: | No |
Plan Description: | There is no IPD sharing plan description |
Studies a U.S. FDA-regulated Drug Product: | Yes |
Studies a U.S. FDA-regulated Device Product: | No |
Product Manufactured in and Exported from the U.S.: | No |
Hypertension Diuretic Comparative Effectiveness Research Point of Care Research |
Hypertension Vascular Diseases Cardiovascular Diseases Hydrochlorothiazide Chlorthalidone Antihypertensive Agents |
Diuretics Natriuretic Agents Physiological Effects of Drugs Sodium Chloride Symporter Inhibitors Membrane Transport Modulators Molecular Mechanisms of Pharmacological Action |