title: Medication safety and chronic kidney disease in older adults prescribed metformin: a cross-sectional analysis.
abstract: BACKGROUND
  Medication 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.
  
  
  METHODS
  We 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.
  
  
  RESULTS
  Among 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).
  
  
  CONCLUSIONS
  CKD 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.
authors.affiliation: Division of General Internal Medicine, University of Washington, Box 354765, 4245 Roosevelt Way NE, Seattle, WA 98105, USA. huangdx@uw.edu.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Huang
authors.forename: Itamar B
authors.initials: IB
authors.lastname: Abrass
authors.forename: Bessie A
authors.initials: BA
authors.lastname: Young
mesh_terms: D000368:Aged; D000075202:Contraindications; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000188:drug therapy*; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects*; D006801:Humans; D007004:Hypoglycemic Agents; D057970:Inappropriate Prescribing / Q000706:statistics & numerical data*; D008297:Male; D008687:Metformin / Q000627:therapeutic use; D051436:Renal Insufficiency, Chronic / Q000139:chemically induced* / Q000150:complications / Q000175:diagnosis*; D012307:Risk Factors; D016896:Treatment Outcome; D014861:Washington
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin