This is the first study in the peer-reviewed literature to report the use of medication cost-cutting behaviors specifically among Medicare Part D beneficiaries with diabetes, and to what extent these behaviors are associated with drug benefits of varying generosity during the coverage gap. Our data indicate that generic-only coverage significantly attenuates the reduction in filled prescriptions after reaching the gap among all Part D beneficiaries, but this finding is limited to the subgroup of participants who use insulin. Although generic-only coverage is associated with a lower likelihood of CRN among insulin users, approximately 15% of all beneficiaries with generic-only coverage still report CRN. Generic-only coverage during the gap did not change the proportion of beneficiaries who reported having to go without basic necessities to pay for their medications.
Our finding of frequent CRN among insulin users with a coverage gap likely reflects the lack of alternative therapeutic options for these patients, who have likely already failed oral anti-glycemic therapy. There are no generic, less expensive versions of any biologic agents including insulin, so insulin users face a steep increase in out-of-pocket medication costs during the gap. If they are unable to afford all of their medications during the gap, these patients may use less of their other medications than prescribed, or in some cases even cut down on the amount of insulin they use. While there are no published papers examining this issue, our findings are consistent with a recent abstract showing that 24% of insulin users who had a coverage gap discontinued at least one medication during the gap.20
The somewhat lower rates of CRN that we observed among insulin users with generic-only coverage in the gap may be due to an indirect benefit from savings on other, generic medications resulting in lower total out-of-pocket costs.
The number of Medicare Part D plans providing generic-only gap coverage has increased in recent years, from 13% of PDPs and 23% of MAPD plans in 2006 to 25% and 34% respectively in 2009.15
The value of this coverage has been debated, since the higher premiums charged to patients, particularly by PDP plans that serve the majority of Medicare beneficiaries, may outweigh the financial benefits expected during the coverage gap.16,21
Premiums for generic-only coverage are generally lower in MAPD plans, since the plans are able to subsidize the cost of providing generic-only gap coverage with revenues they receive for providing other Medicare services within an integrated system. Insulin users, who have high out-of-pocket medication costs during the gap, represent a group of patients for whom higher premiums associated with generic-only coverage may be worthwhile, in terms of providing savings on other medications and reducing overall costs. Additional studies are needed to evaluate these findings in other settings, including the specific cost savings to the patient with different monthly Part D premiums and different types of medication regimens.
Other, more direct options to address the issue of CRN among older adults with diabetes include either providing generic insulin or covering brand name medications during the gap. Existing laws prohibit generic drug manufacturers from marketing biologic agents such as insulin in the United States. Even if pending legislation that would enable the production of generic insulin were to pass,22,23
the medications would not be available to consumers for several years. On the other hand, providing gap coverage for generics as well as some “essential” brand name medications for compounds without generic equivalents would also be effective in minimizing CRN and financial hardship strategies. This type of benefit design, a variant of “reference pricing” used in many other countries,24,25
provides a financial incentive for patients in the gap to choose a cheaper generic over a more expensive, “non-preferred” brand name equivalent, while still covering other brand name prescriptions. While no plans offered this type of gap coverage in 2006, 4% of MAPD plans are providing it during 2009.15
Future studies should investigate the effectiveness of this design as it relates to medication-taking decisions and behaviors.
Our study has several limitations. First, as with several prior studies that surveyed Medicare beneficiaries, we relied solely on patients’ self report of medication cost-cutting behaviors. These patient reports may have been influenced by recall bias. Second, we cannot determine whether cost-cutting behaviors took place before, during, and/or after the coverage gap. However, since some patients may have preemptively decreased their medication use in an attempt to delay or avoid the gap altogether, cost-cutting behaviors reported gap entry may have been attributable to the coverage gap. Our results were also similar after excluding patients who exited the gap and entered catastrophic coverage. Third, our results reflect patients enrolled in one health system and may not be generalizable to other systems with different formularies, deductibles, or other design features. Fourth, we used census-tract level income data as a proxy for individual income in a small minority of cases. Fifth, patients who did not fill any prescriptions in 2006 were excluded from the sampling frame. Finally, this was a non-randomized study and there may be unmeasured group differences between beneficiaries who selected the standard gap plan and those who selected the generic-only plan. We did not see significant differences between the groups in terms of observable clinical characteristics such as self-rated health, number of comorbidities, and number of medications. To mitigate potential selection bias, we controlled for these characteristics and also focused on comparisons within a single health system. To the extent that patients with greater medication needs and costs chose more generous plans, unmeasured selection may remain but would likely exaggerate group differences and would suggest even less of an advantage for beneficiaries to have the generic-only plan.
In conclusion, our results suggest that generic-only coverage during the Part D gap is associated with protection against cost pressures with respect to any CRN, for patients with diabetes who are taking insulin. This may be due to savings on other, generic medications that reduce the total out-of-pocket medication costs faced by insulin users during the gap. Generic-only coverage is not associated with protection against forgoing necessities, compared to the standard coverage gap. Future research should investigate the effectiveness of health plan efforts to educate beneficiaries with diabetes about their prescription drug options, as well as the effects of alternative designs such as covering both generics and essential brand-name medications such as insulin in the coverage gap.