title: Age- and gender-related use of low-dose drug therapy: the need to manufacture low-dose therapy and evaluate the minimum effective dose.
abstract: OBJECTIVE
  Low-dose drug therapy is promoted as a way to maximize benefit and minimize adverse drug effects when prescribing for older adults. This population-based study evaluates the age and sex-related use of two common therapies: thiazide diuretics, where evidence supports the use of low-dose therapy, and beta-blockers, where trials have not evaluated the minimum effective dose.
  
  
  METHODS
  Using linked administrative databases we identified all of the 120,613 persons dispensed a thiazide diuretic therapy and 12,908 myocardial infarction survivors dispensed beta-blocker therapy in Canada's largest province. We used logistic regression models to study the association of age and sex with dispensing of low-dose thiazide diuretic and beta-blocker therapy at doses lower than evaluated in trials.
  
  
  RESULTS
  Of 120,613 older people dispensed a thiazide diuretic, 32,372 (26.8%) were dispensed a low dose. Patients 85 years of age or older, relative to the youngest group, were 30% more likely to be dispensed low-dose therapy (OR=1.31; 95% CI, 1.27 to 1.36; P < .001). Women were 8% more likely than men to be dispensed a low-dose thiazide diuretic (OR=1.08; 95% CI, 1.05 to 1.11; P < .001). Of 10,991 myocardial infarction survivors dispensed atenolol, metoprolol, propranolol, or timolol, 9458 (86.1%) were dispensed a lower-than-evaluated dose. Patients 85 years of age or older, relative to those in the youngest group, were more than twice as likely to be dispensed a lower-than-evaluated beta-blocker therapy dose (OR=2.28; 95% CI, 1.74 to 3.04; P < .001). No difference was noted in the use of beta-blocker therapy dose by sex (OR=1.0; 95% CI, .89 to 1.15; P = .95).
  
  
  CONCLUSIONS
  Low-dose thiazide diuretic therapy prescribed widely to older people, particularly those of advanced age and women. The vast majority of myocardial infarction survivors were dispensed beta-blocker therapy at lower-than-evaluated doses. These findings highlight the need to manufacture low-dose thiazide diuretic therapy and to evaluate the minimum effective dose of beta-blocker therapy.
authors.affiliation: Kunin-Lunenfeld Applied Research Unit, Baycrest Centre for Geriatric Care, University of Toronto, Ontario, Canada.
authors.forename: P A
authors.initials: PA
authors.lastname: Rochon
authors.forename: G M
authors.initials: GM
authors.lastname: Anderson
authors.forename: J V
authors.initials: JV
authors.lastname: Tu
authors.forename: J H
authors.initials: JH
authors.lastname: Gurwitz
authors.forename: J P
authors.initials: JP
authors.lastname: Clark
authors.forename: N H
authors.initials: NH
authors.lastname: Shear
authors.forename: P
authors.initials: P
authors.lastname: Lau
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000008:administration & dosage* / Q000737:chemistry; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001262:Atenolol / Q000008:administration & dosage; D002752:Chlorthalidone / Q000008:administration & dosage; D016001:Confidence Intervals; D019992:Databases as Topic; D004232:Diuretics / Q000008:administration & dosage; D004339:Drug Compounding; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D006852:Hydrochlorothiazide / Q000008:administration & dosage; D016015:Logistic Models; D008297:Male; D008788:Metolazone / Q000008:administration & dosage; D008790:Metoprolol / Q000008:administration & dosage; D009203:Myocardial Infarction / Q000188:drug therapy; D016017:Odds Ratio; D009864:Ontario; D011433:Propranolol / Q000008:administration & dosage; D012189:Retrospective Studies; D012737:Sex Factors; D049993:Sodium Chloride Symporter Inhibitors / Q000008:administration & dosage* / Q000009:adverse effects / Q000737:chemistry; D013999:Timolol / Q000008:administration & dosage
chemical_list: D000319:Adrenergic beta-Antagonists; D004232:Diuretics; D049993:Sodium Chloride Symporter Inhibitors; D006852:Hydrochlorothiazide; D001262:Atenolol; D013999:Timolol; D011433:Propranolol; D008790:Metoprolol; D002752:Chlorthalidone; D008788:Metolazone