Age‐ and Gender‐Related Use of Low‐Dose Drug Therapy: The Need to Manufacture Low‐Dose Therapy and Evaluate the Minimum Effective Dose

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Abstract
OBJECTIVES 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. DESIGN 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.