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Generic Initiation and Adherence to Antidepressant Therapy under Medicare Part D
  • Published Date:
    Dec 2013
  • Source:
    Am J Manag Care. 19(12):989-998.
Filetype[PDF - 898.62 KB]

  • Pubmed ID:
  • Pubmed Central ID:
  • Description:

    To assess the effect of initiating antidepressant therapy with a generic prescription on adherence to antidepressant therapy among Medicare patients. A second objective is to assess how the effect might be moderated by the Medicare Part D coverage gap.

    Research Design

    Adherence to antidepressant therapy was measured by (a lack of) disruption in medication use defined by a gap of >=30 days in antidepressant possession and monthly days of possession, both measured over 180 days since antidepressant initiation. We used a 5% random sample of Medicare fee-for-service beneficiaries who received a new depression diagnosis in the first half of 2007 and initiated antidepressant therapy within 60 days (n=16,778). We estimated a Cox proportional hazard model for antidepressant disruption and a mixed-effects linear model for monthly possession. All analyses were stratified by four cohorts defined by Part D low-income subsidy (LIS) status and Medicare entitlement (aged vs. disabled).


    Generic initiation was associated with improved adherence among all four cohorts, with a stronger effect among the non-LIS patients. Hazard ratios for antidepressant disruption ranged from 0.71 (95% CI: 0.53 to 0.96) among the non-LIS, disabled to 0.88 (95% CI: [0.79, 0.98]) among the LIS, aged. Generic initiation was associated with increases in days of monthly possession in all four cohorts and an additional benefit during the coverage gap for non-LIS patients.


    Generic initiation can be an important tool to improve adherence to antidepressant treatment among Medicare patients and to mitigate the negative effects of the Part D coverage gap.

  • Document Type:
  • Collection(s):
  • Funding:
    K01 MH090087/MH/NIMH NIH HHS/United States
    R01 AG034056/AG/NIA NIH HHS/United States
    P30 MH090333/MH/NIMH NIH HHS/United States
    K01 HS018546/HS/AHRQ HHS/United States
    P30 MH085943/MH/NIMH NIH HHS/United States
    UL1 RR024156/RR/NCRR NIH HHS/United States
    U18 HS016097/HS/AHRQ HHS/United States
    U48 DP001918/DP/NCCDPHP CDC HHS/United States
    R34 MH082682/MH/NIMH NIH HHS/United States
    R01 HS017695/HS/AHRQ HHS/United States
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