title: Medication oversupply in patients with diabetes.
abstract: BACKGROUND
  Studies in integrated health systems suggest that patients often accumulate oversupplies of prescribed medications, which is associated with higher costs and hospitalization risk. However, predictors of oversupply are poorly understood, with no studies in Medicare Part D.
  
  
  OBJECTIVE
  The aim of this study was to describe prevalence and predictors of oversupply of antidiabetic, antihypertensive, and antihyperlipidemic medications in adults with diabetes managed by a large, multidisciplinary, academic physician group and enrolled in Medicare Part D or a local private health plan.
  
  
  METHODS
  This was a retrospective cohort study. Electronic health record data were linked to medical and pharmacy claims and enrollment data from Medicare and a local private payer for 2006-2008 to construct a patient-quarter dataset for patients managed by the physician group. Patients' quarterly refill adherence was calculated using ReComp, a continuous, multiple-interval measure of medication acquisition (CMA), and categorized as <0.80 = Undersupply, 0.80-1.20 = Appropriate Supply, >1.20 = Oversupply. We examined associations of baseline and time-varying predisposing, enabling, and medical need factors to quarterly supply using multinomial logistic regression.
  
  
  RESULTS
  The sample included 2519 adults with diabetes. Relative to patients with private insurance, higher odds of oversupply were observed in patients aged <65 in Medicare (OR = 3.36, 95% CI = 1.61-6.99), patients 65+ in Medicare (OR = 2.51, 95% CI = 1.37-4.60), patients <65 in Medicare/Medicaid (OR = 4.55, 95% CI = 2.33-8.92), and patients 65+ in Medicare/Medicaid (OR = 5.73, 95% CI = 2.89-11.33). Other factors associated with higher odds of oversupply included any 90-day refills during the quarter, psychotic disorder diagnosis, and moderate versus tight glycemic control.
  
  
  CONCLUSIONS
  Oversupply was less prevalent than in previous studies of integrated systems, but Medicare Part D enrollees had greater odds of oversupply than privately insured individuals. Future research should examine utilization management practices of Part D versus private health plans that may affect oversupply.
authors.affiliation: Center for Health Equity Research and Promotion, Veterans Affairs Pittsburgh Healthcare System, University Drive (151C), Building 30, Pittsburgh, PA 15240-1001, USA; Department of Pharmacy and Therapeutics, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA. Electronic address: ctthorpe@pitt.edu.
authors.forename: Carolyn T
authors.initials: CT
authors.lastname: Thorpe
authors.affiliation: Department of Medicine, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA.
authors.forename: Heather
authors.initials: H
authors.lastname: Johnson
authors.affiliation: Pharmacy Society of Wisconsin, 701 Heartland Trail, Madison, WI 53717, USA.
authors.forename: Anna Legreid
authors.initials: AL
authors.lastname: Dopp
authors.affiliation: Center for Health Equity Research and Promotion, Veterans Affairs Pittsburgh Healthcare System, University Drive (151C), Building 30, Pittsburgh, PA 15240-1001, USA; Department of Pharmacy and Therapeutics, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Thorpe
authors.affiliation: Department of Population Health Sciences, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA.
authors.forename: Katie
authors.initials: K
authors.lastname: Ronk
authors.affiliation: Department of Community and Family Medicine, Duke University Medical Center, 318 Hanes House, DUMC 2914, Durham, NC 27710, USA.
authors.forename: Christine M
authors.initials: CM
authors.lastname: Everett
authors.affiliation: Department of Population Health Sciences, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA.
authors.forename: Mari
authors.initials: M
authors.lastname: Palta
authors.affiliation: School of Pharmacy, University of Wisconsin, 777 Highland Drive, Madison, WI 53705, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Mott
authors.affiliation: School of Pharmacy, University of Wisconsin, 777 Highland Drive, Madison, WI 53705, USA.
authors.forename: Betty
authors.initials: B
authors.lastname: Chewning
authors.affiliation: Department of Pharmacy and Therapeutics, University of Pittsburgh, 3501 Terrace Street, Pittsburgh, PA 15261, USA.
authors.forename: Loren
authors.initials: L
authors.lastname: Schleiden
authors.affiliation: Department of Population Health Sciences, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA; Department of Family Medicine, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA; Department of Surgery, University of Wisconsin, 800 University Bay Drive, Suite 210, Madison, WI 53705, USA.
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Smith
mesh_terms: D000367:Age Factors; D000368:Aged; D000959:Antihypertensive Agents / Q000600:supply & distribution; D015331:Cohort Studies; D003920:Diabetes Mellitus / Q000188:drug therapy*; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D004363:Drug Utilization / Q000706:statistics & numerical data; D057286:Electronic Health Records; D005260:Female; D006801:Humans; D007004:Hypoglycemic Agents / Q000600:supply & distribution; D000960:Hypolipidemic Agents / Q000600:supply & distribution; D038801:International Classification of Diseases; D008297:Male; D054524:Medicare Part D; D055118:Medication Adherence; D008875:Middle Aged; D055553:Prescription Drugs / Q000600:supply & distribution*; D012189:Retrospective Studies; D012737:Sex Factors; D014481:United States; D014922:Wisconsin
chemical_list: D000959:Antihypertensive Agents; D007004:Hypoglycemic Agents; D000960:Hypolipidemic Agents; D055553:Prescription Drugs
keywords: Diabetes; Medication surplus; Oversupply; Refill adherence