title: Evaluation of the efficacy and safety of a hydrochlorothiazide to chlorthalidone medication change in veterans with hypertension.
abstract: BACKGROUND
  There are few data available examining the clinical impact of switching patients from hydrochlorothiazide (HCTZ) to chlorthalidone for blood pressure management.
  
  
  OBJECTIVE
  The goal of this study was to compare within-patient clinic blood pressure readings, serum electrolyte levels, and renal function markers before and after a medication change from HCTZ to chlorthalidone in a veteran population.
  
  
  METHODS
  This was a retrospective, pre- and postmeasure, self-controlled study. Veterans Affairs Ann Arbor Healthcare System patients switched from HCTZ to chlorthalidone between January 1, 2001, and January 31, 2012, who had at least 1 follow-up clinic blood pressure reading recorded between 2 and 8 weeks from the date of the medication change were included in the study. Mean pre- and postmeasure values for systolic and diastolic clinic blood pressures, serum potassium, serum sodium, serum calcium, serum creatinine, and blood urea nitrogen were compared by using a 2-tailed, paired t test with a significance level (α) of 0.05.
  
  
  RESULTS
  Of the 40 patients included in the study 95% were male, 65% were white, and the mean age was 64.9 (10.8) years. Both mean systolic (-15.8 mm Hg [95% CI, 8.9 to 22.6], P < 0.0001) and mean diastolic (-4.2 mm Hg [95% CI, 1.5 to 6.9], P = 0.0035) blood pressures showed statistically and clinically significant reductions after the medication change. A statistically significant decrease in mean sodium (-1.1 mmol/L [95% CI, 0.4 to 1.9], P = 0.003) and an increase in mean serum creatinine (0.06 mg/dL [95% CI, -0.09 to -0.02], P = 0.002) was observed; however, these changes may not be viewed as clinically significant by many practitioners. No statistically significant changes were observed in any of the other outcomes examined. Most patients (38 of 40) were taking at least 1 additional antihypertensive agent; 73% of patients were using ≥ 3 antihypertensive agents at the time of the medication change.
  
  
  CONCLUSIONS
  In patients with hypertension already taking HCTZ, switching to chlorthalidone seems to further reduce systolic and diastolic blood pressures without any clinically significant changes in renal function or electrolyte levels.
authors.affiliation: Veterans Affairs Ann Arbor Healthcare System, Ann Arbor, Michigan. Electronic address: kathleen.matthews2@va.gov.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Matthews
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Brenner
authors.forename: Allison C
authors.initials: AC
authors.lastname: Brenner
mesh_terms: D000368:Aged; D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001806:Blood Urea Nitrogen; D002118:Calcium / Q000097:blood; D002752:Chlorthalidone / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D006852:Hydrochlorothiazide / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D006973:Hypertension / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000097:blood; D012189:Retrospective Studies; D016896:Treatment Outcome; D014481:United States; D014728:Veterans
chemical_list: D000959:Antihypertensive Agents; D006852:Hydrochlorothiazide; D003404:Creatinine; D002752:Chlorthalidone; D011188:Potassium; D002118:Calcium
keywords: Veterans Affairs; blood pressure; chlorthalidone; drug toxicity; hydrochlorothiazide; hypertension