Substitution, Spending Offsets, and Prescription Drug Benefit Design

Many U.S. employers have recently adopted less generous prescription drug benefits. In addition, in 2006 the U.S. began to offer prescription drug insurance to approximately 42 million Medicare beneficiaries. We used data on individual health insurance claims and benefit data from 1997 to 2003 to study how changes in consumers' co-payments for prescription drugs affect use of and expenditure on prescription drugs, inpatient care, and outpatient care. We analyzed the effects both in the year of the co-payment change and in the year following the change. Our results show that increases in prescription drug prices reduce both use of and spending on prescription drugs. They also show that consumers substitute the use of outpatient care for prescription drug use and that about 35% of the expenditure reductions on prescription drugs are offset by increases in other spending.