In this nationally representative sample of elderly Medicare beneficiaries with hypertension, we studied the use of multisource cardiovascular drugs—chemically equivalent brand name and generic drugs—and found that most individuals used at least one generic agent. Yet, brand name agents were commonly used when their generic equivalents were available. Indeed, among the individuals in our study using multisource ACE-inhibitors, calcium channel blockers, and alpha-blockers, only one-third to one-half used generic agents, a finding consistent with prior research.11
Since physicians express concern about the cost of medications for their patients,24, 25
one might expect a greater tendency toward use of cost-effective drugs for low-income patients, for whom out-of-pocket costs are more burdensome. We did observe such a pattern of generic medication use, although the magnitude of the association between income and generic use was surprisingly small. For example, after adjusting for confounding variables, we found that individuals with below poverty level incomes were only 40% more likely to receive generics than those with incomes 3 times the poverty level. In addition, individuals who lacked prescription drug coverage also had a modestly greater probability of generic medication use, 29%, compared to those with prescription coverage (from current or former employers). The smaller than expected differences in generic use between those with employer-sponsored coverage and those without prescription coverage may be due in part to the widespread use of drug formularies in retiree benefits packages.26
Nonetheless, the absolute rates of generic use among multisource cardiovascular medications was high for individuals with employer-sponsored coverage, ranging from 30% for beta-blockers to 42% for calcium channel blockers.
Taken together, our findings suggest that opportunities exist to increase use of generic cardiovascular drugs among elderly patients, and potentially reduce their out-of-pocket drug spending. This observation is supported by recent studies which examine the potential savings from generic substitution. Using data from the Medical Expenditure Panel Survey, Haas and colleagues found that 35% of multisource cardiac drugs were dispensed to adults as generics, and estimated that $1.93 billion could be saved through generic substitution of these agents.11
Fischer and colleagues reported savings of up to 30% with generic substitution of multisource cardiovascular drugs in state Medicaid programs12, 17
and higher in one state's pharmaceutical assistance program.17
We note, however, that the potential for increasing rates of generic substitution may vary under different circumstances, such as by type of insurer or region. Using data from a single pharmacy benefits manager (1999-2000) for private retiree plans, Ritter et al found that 91% of multisource drugs were dispensed as generics.27
. Pharmacy data from a single Midwestern state similarly found that 84% of multisource drugs were dispensed as generics.13
The basis for variation in generic substitution is not entirely clear, but the variation should put physicians and policy makers alert to the possibility that a prescription written for a brand name multisource drug will not necessarily be substituted with a generic.
Our findings also imply that those with low incomes and no prescription coverage stand to benefit the most since low-income seniors have the highest rates of medication skipping because of costs.1, 28, 29
As estimated by Haas and colleagues, substituting generic drugs for brand name equivalents could result in moderate to substantial savings on medications for older patients (up to $241 annually),11
savings that are likely to have a considerable impact on use of medications by financially vulnerable seniors.3, 7, 30, 31
The impact on savings through expanded use of generic medications may be especially large for Medicare Part D enrollees since selecting plans that cover brand name agents could inadvertently lead Medicare beneficiaries to enroll in higher cost PDPs (higher premiums, deductibles, and copayments).32
Two additional observations from these data deserve mention. First, we found that VA users had the highest rates of generic use among users of multisource drugs and were the only individuals with consistently high rates of generic use across the 5 drug classes studied. The VA is able to achieve this high level of generic use through its National Drug Formulary, which emphasizes use of generic medications and employs a combination of open, closed, and preferred formulary structures to guide prescribing and obtain discounts from manufacturers.33, 34
A study conducted by the Institute of Medicine found that the VA National Drug Formulary did not result in compromised quality of care for veterans.34
Second, higher levels of medication use were associated with a greater likelihood of using generics. Using more medications may present a greater number of opportunities for introducing generics into a medication regimen, or it may increase the need to minimize medication costs, thereby promoting use of generics.
Policy issues, like formularies and state laws that mandate use of generics for Medicaid beneficiaries, are probably the most influential factors determining use of generic medications among the elderly. Also, pharmacists are required by the Medicare Modernization Act to discuss generic substitution with Medicare Part D enrollees when such opportunities arise. Yet, even with strong pro-generic policies in place, physician and patient attitudes towards generic drugs may remain an important factor. Some physicians may prefer using brand name drugs, perhaps due to the effect of pharmaceutical marketing,35
or to perceptions about safety and efficacy.22, 24
Indeed, a 1989 study of a nationally representative sample of outpatient visits found that 30% of the residual variability in generic vs. brand name medication use was attributable to physicians.36
Selection of generic medications may also be influenced by physician specialty as specialists are more likely than generalists to adopt the use of novel agents.37
It should be noted, however, that physicians may at times have no preference for a brand name or generic drug, but may be in the habit of referring to a commonly used drug by its brand name name. Negative attitudes towards or misperceptions of generic drugs by patients may also play a role as prior studies have shown that patients often regard generics as riskier to use than brand name drugs.38, 39
For the most part, these studies address attitudes about generics among non-elderly adults in Europe and in a single metropolitan area in the U.S. Additional research is needed in the U.S. to determine older patients' and physicians' roles in the uptake of generic medications.
To our knowledge, this is the first nationally representative study of multisource medication use among elderly Medicare beneficiaries, and the first to specifically examine the associations of income and coverage with generic or brand name multisource drugs. The study has some limitations, however, that warrant discussion. First, we rely on verbatim reports of medication names to determine whether each drug was generic or brand. This approach might result in under-reporting of generic drug use,40
but such under-reporting should not necessarily differ across strata of income and prescription drug coverage, nor should it result in different rates of generic medication use across the 5 classes of drugs we studied. Second, the MCBS does not provide data on the number of prescriptions filled so we were unable to determine the proportion of prescription fills that were generic. Third, the MCBS has no data on the cost-sharing structure of prescription plans, so we can only report the aggregate effect among plan types and may miss details of insurance plans that successfully promote use of generic medications. Fourth, adverse selection could have biased our results if individuals without prescription coverage and those with HMO coverage had less need for medications and did not acquire any or more generous prescription benefits. However, the average number of cardiovascular drugs used by individuals in these groups (1.6 and 1.7, respectively) did not differ substantially from that of individuals in other coverage groups (range of means, 1.6 to 2.0; overall mean 1.7). Thus, it is unlikely that adverse selection greatly biased our estimates of generic use or expenditures. Lastly, we were underpowered to detect statistically significant differences of 10% in use of generic medications by income and prescription drug coverage in many of the subgroup analyses of individual classes of cardiovascular drugs.
In conclusion, our findings indicate that Medicare beneficiaries with hypertension, including those who are most financially vulnerable, underuse generic medications in 3 of 5 classes of cardiovascular medications and are therefore missing opportunities to reduce out-of-pocket spending. Because elderly Medicare beneficiaries burdened by medication costs infrequently tell their doctors about problems paying for medications,41-43
physicians should be ever vigilant about cost-effective prescribing. Moreover, since prescription drug plan medication formularies present a significant burden to many physicians,8
and because Medicare Part D might add to this burden by increasing the number of different formularies in local markets, the surest way for patients to receive the least expensive medications covered by their plans is to prescribe generic agents whenever possible.