Effects of Using Generic Drugs on Medicare's Prescription Drug Spending

September 15, 2010

Four years ago, Medicare began providing outpatient prescription drug benefits for senior citizens and people with disabilities. Known as Part D, the program uses private plans to provide coverage for prescription drugs to enrollees. Those plans negotiate payment rates with pharmacies and rebates from drug manufacturers while competing for enrollees. Such competition provides incentives for plans to control their costs; one important way in which plans seek to control costs is by encouraging the use of generic drugs. A CBO study released today assesses how successful plans have been in encouraging the use of generic drugs and the potential for savings from the additional use of such drugs.

In 2007, total payments to plans and pharmacies from the Part D program and its enrollees were about $60 billion. The total number of prescriptions filled was about 1 billion, of which 65 percent were filled with generic drugs, 5 percent were filled with multiple-source brand-name drugs (brand-name drugs that are also available in generic versions), and 30 percent were filled with single-source brand-name drugs (brand-name drugs for which no chemically equivalent generic versions are available). Even though a majority of prescriptions were filled with generic drugs, their lower prices meant that those prescriptions accounted for only 25 percent of total prescription drug costs.

Potential Savings from Generic Substitution. To control their costs, plans encourage enrollees to switch from brand-name drugs to their less expensive generic equivalents, a practice known as generic substitution. CBO estimates that:

  • Dispensing generic drugs rather than their brand-name counterparts reduced total prescription drug costs in 2007 by about $33 billion, meaning that total payments to plans and pharmacies from the Part D program and its enrollees would have been about $93 billion—or 55 percent higher—if no generics had been available.
  • The potential for additional savings from increased generic substitution is comparatively small, totaling less than $1 billion.

Potential Savings from Therapeutic Substitution. In one form of a practice known as therapeutic substitution, plans can also encourage enrollees to switch from a brand-name drug to the generic form of a different drug that is in the same therapeutic class (that is, a drug designed to treat the same medical condition). To assess the potential for such savings, CBO examined seven therapeutic classes identified by the Medicare program as providing opportunities for such substitution. CBO finds that:

  • If all of the single-source brand-name prescriptions in those seven classes had been switched to generic drugs from the same class, prescription drug costs would have been reduced by $4 billion in 2007.
  • Savings from therapeutic substitution to generic drugs could have been much higher than $4 billion to the extent that other classes of drugs also would have presented options for substitution. The seven classes that CBO evaluated represented only about 15 percent of the cost of single-source brand-name drugs under Part D. However, the potential savings could have been lower than $4 billion because in many cases it would have been medically inappropriate to switch to a generic form of a therapeutically similar drug.

Policymakers would face several challenges in developing tools to achieve any additional savings from the expanded use of generic drugs—particularly in the case of therapeutic substitution. About half of Part D spending is on behalf of enrollees who have lower incomes and thus qualify for additional subsidies. Policies that used financial incentives to steer enrollees toward certain drugs might not be effective for that population because Medicare pays nearly all of their costs.

This study was prepared by Julie Somers of CBO’s Microeconomic Studies Division.