Comparative antihypertensive effects of hydrochlorothiazide and chlorthalidone on ambulatory and office blood pressure.

Abstract

Low-dose thiazide-type diuretics are recommended as initial therapy for most hypertensive patients. Chlorthalidone has significantly reduced stroke and cardiovascular end points in several landmark trials; however, hydrochlorothiazide remains favored in practice. Most clinicians assume that the drugs are interchangeable, but their antihypertensive effects at lower doses have not been directly compared. We conducted a randomized, single-blinded, 8-week active treatment, crossover study comparing chlorthalidone 12.5 mg/day (force-titrated to 25 mg/day) and hydrochlorothiazide 25 mg/day (force-titrated to 50 mg/day) in untreated hypertensive patients. The main outcome, 24-hour ambulatory blood pressure (BP) monitoring, was assessed at baseline and week 8, along with standard office BP readings every 2 weeks. Thirty patients completed the first active treatment period, whereas 24 patients completed both. An order-drug-time interaction was observed with chlorthalidone; therefore, data from only the first active treatment period was considered. Week 8 ambulatory BPs indicated a greater reduction from baseline in systolic BP with chlorthalidone 25 mg/day compared with hydrochlorothiazide 50 mg/day (24-hour mean = -12.4+/-1.8 mm Hg versus -7.4+/-1.7 mm Hg; P=0.054; nighttime mean = -13.5+/-1.9 mm Hg versus -6.4+/-1.8 mm Hg; P=0.009). Office systolic BP reduction was lower at week 2 for chlorthalidone 12.5 mg/day versus hydrochlorothiazide 25 mg/day (-15.7+/-2.2 mm Hg versus -4.5+/-2.1 mm Hg; P=0.001); however, by week 8, reductions were statistically similar (-17.1+/-3.7 versus -10.8+/-3.5; P=0.84). Within recommended doses, chlorthalidone is more effective in lowering systolic BPs than hydrochlorothiazide, as evidenced by 24-hour ambulatory BPs. These differences were not apparent with office BP measurements.

• Authors: Michael E Ernst, Barry L Carter, Chris J Goerdt, Jennifer J G Steffensmeier, Beth Bryles Phillips, M Bridget Zimmerman, George R Bergus
• Journal: Hypertension (Dallas, Tex. : 1979) (Hypertension) Vol. 47 Issue 3 Pg. 352-8 (Mar 2006) ISSN: 1524-4563 [Electronic] United States
• PMID: 16432050 (Publication Type: Journal Article, Randomized Controlled Trial, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Sodium Chloride Symporter Inhibitors
• Hydrochlorothiazide
• Chlorthalidone

Topics

• Adult
• Blood Pressure (drug effects)
• Blood Pressure Determination (methods)
• Blood Pressure Monitoring, Ambulatory
• Chlorthalidone (administration & dosage, adverse effects, therapeutic use)
• Cross-Over Studies
• Drug Administration Schedule
• Drug Interactions
• Female
• Humans
• Hydrochlorothiazide (administration & dosage, adverse effects, therapeutic use)
• Hypertension (diagnosis, drug therapy, physiopathology)
• Male
• Middle Aged
• Office Visits
• Single-Blind Method
• Sodium Chloride Symporter Inhibitors (administration & dosage, adverse effects, therapeutic use)
• Time Factors