Generous Insurance May Promote More Expensive Drugs
A February 18 Web-only report in Health Affairs said that the decision of whether to prescribe a cyclooxygenase type 2 (COX-2) inhibitor for osteoarthritis—apparently instead of a less-expensive nonselective nonsteroidal antiinflammatory drug (NSAID)—depends largely on the generosity of the patient's drug benefit, not the true need for the more-expensive product.
In general, nonselective NSAIDs are preferred over COX-2 inhibitors as initial therapy in patients who are not at high risk for gastrointestinal (GI) adverse events. The Health Affairs report examined COX-2 inhibitor use among 4,601 Medicare beneficiaries during 2000, when the products were well established in the market and concerns about their adverse cardiovascular effects had not yet appeared in the scientific literature.
According to the report, 26 percent of the Medicare beneficiaries with the "most generous" drug benefit received a COX-2 inhibitor to treat osteoarthritis, compared with 13 percent of Medicare beneficiaries with no drug coverage.
The study found an expected association between a patient's GI adverse-event risk and COX-2 inhibitor prescribing. According to the report, Medicare beneficiaries in the highest GI risk group were 50 percent more likely than those in the lowest risk group to be prescribed a COX-2 inhibitor. But the report stated that the generosity of the patient's drug benefit "substantially mediates the odds of being prescribed a COX-2 [inhibitor] as a function of GI risk."
The actual use of nonselective NSAIDs by study subjects is unknown, because the Medicare data set used for the analysis did not include information on nonprescription drug use.
Bruce Stuart, director of the Peter Lamy Center on Drug Therapy and Aging at the University of Maryland School of Pharmacy in Baltimore and one of the report's authors, said that the study's findings have implications for the Medicare drug benefit that goes into effect in 2006.
"What this research shows is that drug coverage is, indeed, going to lead to increased use of pharmaceuticals, but it's not clear that it's going to lead, necessarily, to better use of pharmaceuticals," Stuart said.
"I think the results of this [study] can be generalized to, for example, expensive branded products as opposed to generic products," he said. "Unless there are formulary restrictions or copayment penalties for choosing the more expensive products, you can expect that people want the more expensive one."
"This is just human nature," Stuart said.
Stuart and his coauthors relied on a GI-risk scoring system used at Veterans Health Administration (VHA) hospitals to determine whether a patient with osteoarthritis should receive a COX-2 inhibitor. According to the report, VHA may consider COX-2 inhibitors appropriate for patients whose score indicates a "substantial" GI adverse-event risk, as was the case for 22 percent of the patients in the current study.
Sixty percent of the Medicare beneficiaries in the study were at "significant" risk for GI adverse events, a level that VHA deems suitable for COX-2 inhibitor therapy if an NSAID is required for 30 days or longer and the patient did not respond to etodolac or salsalate therapy.
According to the report, the VHA scoring system recommends a nonselective NSAID for patients with "moderate" or lower risk. Twenty percent of the study subjects were considered at moderate risk for GI adverse events. Because all of the patients in the analysis were age 65 years or older, none fell into the lowest possible risk group.
Although VHA is not alone in setting minimum requirements for COX-2 inhibitor use, the health system's selection criteria are more stringent than those used by some pharmacy benefit providers.
For example, the Department of Defense's TRICARE pharmacy program requires prior authorization for the dispensing of a COX-2 inhibitor but classifies patients age 65 years or older as at high risk for GI adverse events and eligible for the selective drugs. Thus, all of the patients in Stuart's study would have met TRICARE's COX-2 inhibitor prescribing criteria by virtue of age alone.
Some insurers set a minimum age of 60 years before waiving the prior authorization requirement for prescribing a COX-2 inhibitor. Others combine age with other requirements.
Stuart said this his study should not be taken as an indication that "there is a lot of waste in the system that needs to be taken care of before we can afford providing expanded drug coverage."
Instead, he said, the study's results are "a cautionary road sign."
"Be careful when you provide greater access" to drugs, he said. "Test your assumptions about what is better" before making decisions about therapy.