Research Activities #285, May 2004

copayments for prescription medications led to decreases in their use of eight classes of therapeutic drugs, according to a new study cofunded by the Agency for Healthcare Research and Quality (HS13447). Researchers linked pharmacy claims data representing nearly 530,000 people aged 18 to 64. All of the subjects had employer-sponsored health insurance, with health benefit designs from 52 private health plans and 30 employers. The study included health insurance plans of all types that had one-tier, two-tier, three-tier, and coinsurance drug benefit plans. The simulated copayment increases were relevant for all plans but were calibrated to two-tier plans. The analysis followed study subjects for nearly 4 years. Based on this analysis, the researchers estimated that doubling copayments in a typical two-tier drug plan resulted in an approximately 45 percent reduction in the use of antiinflammatory drugs and antihistamines, a drop of approximately 35 percent in the use of cholesterol-lowering medications and drugs to treat ulcers and asthma, and a decrease of about 25 percent in the use of medicines for high blood pressure, depression, and diabetes. The rate of decrease depended on whether patients were taking the drug on an ongoing or intermittent basis. Patients with chronic illnesses were less likely to cut back or stop taking the medications needed to treat their conditions when drug copayments increased. However, they seemed to reduce their use of other medications. For example, the study found that patients with depression cut their use of most drugs by 25 percent but reduced their use of antidepressants by only 8 percent when their copayments doubled. Similarly, patients with high blood pressure cut their use of antihypertensives by only 10 percent but reduced their use of all other drugs by 27 percent. Research Activities