Document Detail

Generic alendronate use among Medicare beneficiaries: are Part D data complete?
MedLine Citation:
PMID:  23135758     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: Generic alendronate was approved in the United States on February 6, 2008. Medicare beneficiaries might pay for generic alendronate out-of-pocket without having claims submitted, resulting in misclassification of generic alendronate use in Medicare data.
OBJECTIVES: To estimate the completeness of generic alendronate use in 2008 Medicare Part D data; to identify factors associated with staying on branded alendronate versus switching to a generic product.
METHODS: We identified Medicare beneficiaries highly adherent (medication possession ratio ≥80%) with branded alendronate during 1/1/06-2/6/07 ("2007 cohort") and during 1/1/07-2/6/08 ("2008 cohort"). The outcome was medication status at the end of follow-up (12/31/2007 or 12/31/2008), classified as continued branded alendronate, switched to generic alendronate, switched to another bisphosphonate or presumed discontinued bisphosphonate therapy. Cox regression estimated the hazard ratio (HR) for discontinuation in 2008 compared to 2007. Multinomial logistic regression identified factors associated with medication status for the 2008 cohort.
RESULTS: Among 15,310 subjects using branded alendronate in the 2008 cohort, 81% switched to generic alendronate. The proportion presumably discontinuing bisphosphonate therapy was 8.9% in 2008 compared to 7.7% in the 2007 cohort (adjusted HR, 1.15; 95% confidence interval, 1.05, 1.26). Factors associated with staying on branded alendronate in 2008 were higher income, eligibility for a low income subsidy and use of Fosamax® plus vitamin D.
CONCLUSION: Evaluation of Medicare prescription drug data suggests that the amount of missing claims for generic alendronate in 2008 was not substantial, and misclassification of exposure in studies examining alendronate use post-generic product availability should be minimal.
Huifeng Yun; Jeffrey R Curtis; Kenneth Saag; Meredith Kilgore; Paul Muntner; Wilson Smith; Robert Matthews; Nicole Wright; Michael A Morrisey; Elizabeth Delzell
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2012-11-08
Journal Detail:
Title:  Pharmacoepidemiology and drug safety     Volume:  22     ISSN:  1099-1557     ISO Abbreviation:  Pharmacoepidemiol Drug Saf     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-08     Completed Date:  2013-06-03     Revised Date:  2014-06-12    
Medline Journal Info:
Nlm Unique ID:  9208369     Medline TA:  Pharmacoepidemiol Drug Saf     Country:  England    
Other Details:
Languages:  eng     Pagination:  55-63     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 John Wiley & Sons, Ltd.
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MeSH Terms
Aged, 80 and over
Alendronate / administration & dosage,  economics,  therapeutic use*
Bone Density Conservation Agents / administration & dosage,  economics,  therapeutic use*
Drug Approval
Drug Substitution / economics,  statistics & numerical data
Drugs, Generic / administration & dosage,  economics,  therapeutic use*
Follow-Up Studies
Logistic Models
Medicare Part D / economics,  statistics & numerical data*
Proportional Hazards Models
Socioeconomic Factors
United States
Grant Support
Reg. No./Substance:
0/Bone Density Conservation Agents; 0/Drugs, Generic; X1J18R4W8P/Alendronate

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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