Abstract
BackgroundMedication safety in patients with chronic kidney disease (CKD) is a growing concern. This is particularly relevant in older adults due to underlying CKD. Metformin use is contraindicated in patients with abnormal kidney function; however, many patients are potentially prescribed metformin inappropriately. We evaluated the prevalence of CKD among older adults prescribed metformin for type 2 diabetes mellitus using available equations to estimate kidney function and examined demographic characteristics of patients who were potentially inappropriately prescribed metformin.MethodsWe conducted a cross-sectional analysis of older adults aged ≥65 years prescribed metformin from March 2008-March 2009 at an urban tertiary-care facility in Seattle, Washington, USA. CKD was defined using National Kidney Foundation-Kidney Disease Outcomes Quality Initiative criteria. Creatinine clearance was calculated using the Cockcroft-Gault equation; estimated glomerular filtration rate was calculated using the abbreviated Modification of Diet in Renal Disease (MDRD) and CKD-Epidemiology (EPI) Collaboration equations. Regression analyses were used to determine the associations between demographic characteristics and prevalent CKD.ResultsAmong 356 subjects (median age 69 years, 52.5% female, 39.4% non-Hispanic black), prevalence of stage 3 or greater CKD calculated by any of the equations was 31.4%. The Cockcroft-Gault equation identified more subjects as having CKD (23.7%) than the abbreviated MDRD (21.1%) or CKD-EPI (21.7%) equations (P < 0.001). Older age (OR = 1.13, 95% CI 1.08-1.19) and female sex (OR = 2.51, 95% CI 1.44-4.38) were associated with increased odds of potentially inappropriate metformin prescription due to CKD; non-Hispanic black race was associated with decreased odds of potentially inappropriate metformin prescription due to CKD (OR = 0.41, 95% CI 0.23-0.71).ConclusionsCKD is common in older adults prescribed metformin for type 2 diabetes, raising concern for potentially inappropriate medication use. No single equation to estimate kidney function may accurately identify CKD in this population. Medication safety deserves greater consideration among elderly patients due to the widespread prevalence of CKD.
Highlights
Medication safety in patients with chronic kidney disease (CKD) is a growing concern
New CKD estimating equations such as the abbreviated Modification of Diet in Renal Disease (MDRD) Study equation [1] and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula [2] are available, pharmacists tasked with the delivery of medications tend to use the older Cockcroft-Gault formula [3] to estimate CKD according to pharmaceutical manufacturer recommendations [4]
The current study reports the prevalence of CKD among older adults with type 2 diabetes mellitus prescribed metformin at an urban tertiarycare facility and compares the prevalence of CKD using the Cockcroft-Gault, abbreviated MDRD and CKD-EPI equations to estimate kidney function
Summary
Medication safety in patients with chronic kidney disease (CKD) is a growing concern. This is relevant in older adults due to underlying CKD. Metformin use is contraindicated in patients with abnormal kidney function; many patients are potentially prescribed metformin inappropriately. We evaluated the prevalence of CKD among older adults prescribed metformin for type 2 diabetes mellitus using available equations to estimate kidney function and examined demographic characteristics of patients who were potentially inappropriately prescribed metformin. Medication safety in older adults is a growing concern, in those with chronic kidney disease (CKD). Metformin is an effective medication commonly prescribed to treat type 2 diabetes mellitus, but its use is potentially limited in adults ≥65 years of age due to increased prevalence of CKD [5,6]. Older adults are at higher risk of developing adverse events when using metformin due to underlying impaired kidney function
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