A very small percentage of people receiving prescription drug benefits are responsible for a significant proportion of drug spending, a new study suggests.

Very high-cost patients are defined as those responsible for a minimum of $174 a month in pharmacy costs. The study by Express Scripts, a pharmacy benefits manager, found that:

• More than 50 percent of drug expenditures are attributable to five percent of its members.

• The top two percent of patients are "very high-cost" users, accounting for 33 percent of prescription drug expenditures, it said.

• Furthermore, high-cost patients remained high-cost from one year to the next; of patients in the high-cost category in 1998, 75 percent remained high-cost in 1999.

Most high-cost patients have conditions like cancer, diabetes or heart disease, and they are using drugs in multiple classes.

The highest-cost adult patients have very high use rates for certain drug classes. For example, 48 percent use antidepressants or anti-anxiety medications, 40 percent use anti-ulcer drugs and 59 percent use drugs for treating high blood pressure.

The highest cost patients also are more likely to fill prescriptions with branded products, mostly because they are taking drugs for which there is no chemically equivalent generic available.

Source: Kathleen Fairman, "Fact Sheet: Understanding the High-Cost Patient," Outcomes Conference 2001, June 19, 2001, Express Scripts; "Targeting high-cost patients may cut drug spending," Reuters Health, June 20, 2001.