title: Hydrochlorothiazide versus chlorthalidone: evidence supporting their interchangeability.
abstract: Thiazide diuretics are one of the preferred pharmacologic treatments for hypertension. Hydrochlorothiazide and chlorthalidone have been the 2 most commonly used diuretics in major clinical trials. Treatment guidelines and compendia often consider these 2 drugs interchangeable agents within the class of thiazide or thiazide-like diuretics. Many sources list them as equipotent. Despite these beliefs, there is some suggestion that cardiovascular outcomes are not necessarily the same with these 2 drugs. We conducted a literature search from 1960 to 2003 to identify studies that evaluated the pharmacokinetic and blood pressure-lowering effects of these 2 agents. There are significant pharmacokinetic and pharmacodynamic differences between these diuretics. Chlorthalidone is approximately 1.5 to 2.0 times as potent as hydrochlorothiazide, and the former has a much longer duration of action. Whether these pharmacokinetic and pharmacodynamic features cause differences in outcomes is not known.
authors.affiliation: Division of Clinical and Administrative Pharmacy, College of Pharmacy, Building S 532, University of Iowa, Iowa City, IA 52242, USA. barry-carter@uiowa.edu
authors.forename: Barry L
authors.initials: BL
authors.lastname: Carter
authors.forename: Michael E
authors.initials: ME
authors.lastname: Ernst
authors.forename: Jerome D
authors.initials: JD
authors.lastname: Cohen
mesh_terms: D000959:Antihypertensive Agents / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D002752:Chlorthalidone / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D002986:Clinical Trials as Topic; D004232:Diuretics; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006852:Hydrochlorothiazide / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use; D006973:Hypertension / Q000188:drug therapy; D049993:Sodium Chloride Symporter Inhibitors / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000627:therapeutic use
chemical_list: D000959:Antihypertensive Agents; D004232:Diuretics; D049993:Sodium Chloride Symporter Inhibitors; D006852:Hydrochlorothiazide; D002752:Chlorthalidone