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The American Journal of Managed Care January 2016
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The Introduction of Generic Risperidone in Medicare Part D
Vicki Fung, PhD; Mary Price, MA; Alisa B. Busch, MD, MS; Mary Beth Landrum, PhD; Bruce Fireman, MA; Andrew A. Nierenberg, MD; Joseph P. Newhouse, PhD; and John Hsu, MD, MBA, MSCE
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The Introduction of Generic Risperidone in Medicare Part D

Vicki Fung, PhD; Mary Price, MA; Alisa B. Busch, MD, MS; Mary Beth Landrum, PhD; Bruce Fireman, MA; Andrew A. Nierenberg, MD; Joseph P. Newhouse, PhD; and John Hsu, MD, MBA, MSCE
This study examines the plan characteristics associated with generic risperidone use and spending and adherence outcomes associated with use among Medicare Advantage Part D beneficiaries.
Antipsychotic Adherence and Nonpersistence

Beneficiaries who switched antipsychotics, either to generic risperidone or other brand SGAs, had higher odds of adherence in 2009 versus those who remained on the same brand SGA: odds ratio (OR), 1.72 (95% CI, 1.48-2.00) for bioequivalent generic substitution; OR, 2.34 (95% CI, 1.62-3.40) for nonbioequivalent generic substitution; OR, 1.43 (95% CI, 1.04-1.96) for nonbioequivalent brand switching (Table 3). These beneficiaries also had lower rates of nonpersistence in 2009, defined as the time to first gap in SGA use >30 days, compared with those who continued using the same brand SGA in 2008.

Figure 2 presents within-person changes in the PDC by antipsychotics in each month in 2008 and 2009 relative to June 2008—the month prior to generic introduction. Declines in use toward the end of each calendar year are consistent with the pattern of an increasing number of beneficiaries reaching the coverage gap and losing drug coverage. Those with nonbioequivalent generic substitution had the smallest relative reductions in SGA use by the end of 2009 compared with other beneficiaries (–2.6 percentage points in PDC; 95% CI, –8.3 to 3.0), including those who switched to a different brand SGA (–15.7 percentage points; 95% CI, –20.4 to –10.9); those who stayed on the same brand SGA throughout 2008 had the largest reductions in use by the end of 2009 (–27.5 percentage points; 95% CI, –28.9 to –26.1).

DISCUSSION
This study focused on the effects of the introduction of the first widely used SGA, risperidone, in Medicare Part D. We examined the levels of generic risperidone use in the first 18 months of introduction among beneficiaries receiving ongoing SGA drug therapy. Fewer than 1 in 4 beneficiaries used generic risperidone by the end of the study period, and the vast majority of use was among those previously using brand risperidone. Generic risperidone use was associated with lower total and out-of-pocket antipsychotic spending, as well as higher levels of adherence and persistence to SGA therapy.

The high levels of bioequivalent generic substitution and the limited variation by MA plan type and cost-sharing levels suggest that these switches could happen automatically (eg, generic substitution at the pharmacy). Despite concerns about patient mistrust of generics, bioequivalent generic substitution did not adversely affect adherence, on average. Moreover, bioequivalent generic substitution was associated with savings in total and out-of-pocket antipsychotic spending.

We are not able to determine if beneficiaries used brand risperidone after July 2008 or stopped using SGAs entirely because Part D event data do not capture uncovered drug use. We hypothesize, however, that levels of brand risperidone use were low. We found a similar percent of beneficiaries had no SGA fills after July 2008 across those who were previously using branded risperidone and other SGAs. Moreover, industry reports suggest that levels of brand Risperdal use were minimal after the introduction of generic risperidone.8

The Congressional Budget Office estimates that across all drug classes, Part D could have saved an additional $4 billion through nonbioequivalent generic substitution in 2007.2 However, we found that few beneficiaries (<7%) using other SGAs switched to generic risperidone. Although physicians and patients are hesitant to switch SGAs if patients are stable on existing regimens, we found that even among those who actively switched SGAs only one-third switched to generic risperidone. It is possible that switching to risperidone might not have been clinically appropriate for all of these beneficiaries if some previously experienced poor tolerability or treatment failure with risperidone. In our study population, however, only 6% of beneficiaries who switched to a different brand SGA had any documented use of brand risperidone in the prior year, suggesting potential opportunities for greater nonbioequivalent generic substitution.

Encouraging more nonbioequivalent generic substitution among beneficiaries who require changes in their SGA drug regimen could yield clinical benefits in addition to cost savings. We found that beneficiaries who switched to generic risperidone from other brand SGAs had higher levels of adherence and lower rates of gaps in use in 2009. In addition, we found smaller relative reductions in SGA use over the first 18 months after generic introduction for beneficiaries who switched to generic risperidone compared with those who switched to other brand SGAs. Nevertheless, work is needed to evaluate the clinical effects of nonbioequivalent generic substitution. The recent availability of additional generic SGAs, including olanzapine, ziprasidone, and quetiapine in 2011 and 2012, however, provide a greater range of therapeutic options for generic substitution. This is especially important given the recent proposal by CMS to remove the formulary protections for 3 of the 6 protected drug classes, including antipsychotics.16 Although CMS retracted this proposal after substantial backlash, statute allows for the protections for these classes to be revisited in the future.

We found that HMO plans with tighter and formal physician networks were more effective at encouraging nonbioequivalent generic substitution than private FFS plans without provider networks.12 The Medicare Improvements for Patients and Providers Act required most private FFS plans to establish provider networks starting in 2011, resulting in the withdrawal of many private FFS plans from the market.17,18 The older private FFS model, however, could more closely mirror the experience of beneficiaries enrolled in stand-alone prescription drug plans, which cover about two-thirds of Part D beneficiaries.19

Contrary to our expectations, patient financial incentives, via cost-sharing, to use generic drugs had limited influence on generic substitution rates. These findings differ from evidence in other drug classes, such as hyperlipidemia and hypertension drugs, where incentive-based formularies have been linked with higher rates of switching to lower-tier drugs.20-22 Patient financial incentives could be less effective at encouraging generic use for psychotropic drugs and result in greater cost-shifting to patients, especially for those with serious mental illness where there is greater hesitancy to switch drug regimens if patients are stable.23,24

Limitations

This was a nonrandomized study and there could be unmeasured differences across beneficiaries with different drug use patterns. In particular, beneficiaries with nonbioequivalent changes in their SGA regimens could have worse disease severity or recent exacerbations that could affect their proclivity to adhere to SGAs. In fact, we found higher levels of adherence among beneficiaries who switched to different brand SGA drugs compared with those who remained on the same brand SGA. Similarly, we found no significant difference in total antipsychotic spending for those who switched from other SGAs to generic risperidone compared with those who remained on the same SGA; this is likely due to the higher levels of antipsychotic use.

To address this potential confounding by indication, we compared within-person changes in adherence using fixed effects estimation, which is robust to time-stable confounders across the groups. In addition, we included comparisons between those with nonbioequivalent changes in their SGA drug regimens (ie, those who switched from other SGAs to generic risperidone vs those who switched to a different brand drug). These beneficiaries were more similar with respect to prior year drug spending, comorbidity risk scores, and disability (eAppendix 1 [eAppendices available at www.ajmc.com]). Consistent with our hypotheses, in the fixed effects analyses, we found those who switched from other SGAs to generic risperidone had smaller relative reductions over time in their antipsychotic adherence compared with those who switched to other brand SGAs. We also conducted parallel sensitivity analyses among the subgroup of beneficiaries with documented diagnoses of schizophrenia and bipolar disorder and found consistent results.

Our study is limited to beneficiaries enrolled in MA Part D plans, and may not generalize to those in stand-alone prescription drug plans. Within our study population, there were low levels of PPO enrollment, limiting our ability to estimate the association between PPOs and generic uptake. HMOs and private FFS plans have different geographic patterns (ie, HMOs tend to be offered in urban markets and private FFS plans in rural areas); however, there is overlap between these plan types in small metropolitan areas. Lastly, utilization management requirements, such as prior authorization, can also influence drug choices. All subjects in this study faced similar utilization management requirements (none for the most commonly used SGAs).

Findings from this study also may not generalize to non-Medicare populations, including those in commercial insurance plans or Medicaid (eg, due to differences in the underlying patient 14 populations or the availability and effects of various policy levers to influence generic use). Understanding the implications of generic entry within Medicaid is especially important as SGAs comprised 15% of all Medicaid drug expenditures in 2009.25,26

CONCLUSIONS
In conclusion, generic use of SGAs was concentrated among patients previously using branded risperidone, and Medicare Part D HMO plans appeared to be more effective at encouraging generic use than private FFS plans without formal physician networks. While patient financial incentives had limited influence on switching, lower patient out-of-pocket drug costs associated with generic substitution appeared to be associated with improved patient adherence to SGA treatment. With the recent introduction of additional generic SGAs, considerable opportunity remains to reduce Medicare and beneficiary spending, and potentially improve treatment adherence and outcomes.

Author Affiliations: Department of Psychiatry (AAN) and Mongan Institute for Health Policy (VF, MP, JH), Massachusetts General Hospital, Boston, MA; Department of Medicine (VF, JH), Department of Health Care Policy (ABB, MBL, JPN, JH), and Department of Psychiatry (AAN), Harvard Medical School, Boston, MA; McLean Hospital (ABB), Belmont, MA; Health Services Research Division, Partners Psychiatry & Mental Health (ABB), Boston, MA; Division of Research, Kaiser Permanente Northern California (BF), Oakland, CA; Department of Health Policy and Management, Harvard School of Public Health (JPN), Boston, MA; Harvard Kennedy School, Harvard University (JPN), Cambridge, MA.

Source of Funding: The National Institute of Mental Health (R01MH090284) provided funding for this study.

Author Disclosures: Dr Fung received a grant from NIMH, which funded this study. Dr Newhouse is on the board of Aetna, which sells Part D plans, and also owns Aetna stock. Due to length, Dr Nierenberg’s disclosures/conflicts of interest are available in eAppendix 2. The remaining authors report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.

Authorship Information: Concept and design (VF, ABB, JH, AAN, MBL); acquisition of data (VF, MP, JH); analysis and interpretation of data (VF, JPN, MP, ABB, BF, JH, MBL); drafting of the manuscript (VF, AAN); critical revision of the manuscript for important intellectual content (VF, JPN, ABB, BF, JH, AAN, MBL); statistical analysis (VF, JPN, MP, BF, MBL); provision of patients or study materials (VF, JH); obtaining funding (VF); administrative, technical, or logistic support (VF, MP); and supervision (VF).

Address correspondence to: Vicki Fung, PhD, 50 Staniford St, 9th Fl, Boston, MA 02114. E-mail: vfung@mgh.harvard.edu.
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