Two months in, about 4 million people have cards, but about 3 million of them were enrolled automatically by their HMOs or through state assistance programs.

The drug discount cards, launched in May, were aimed at helping Medicare recipients before the full prescription drug benefit program begins in 2006.

Drug prices vs. savings Comparing drugs in Maryland: Drug Price1 Savings2 Celebrex $198.99 17-20% Fosamax $87.49 17-28% Lipitor $85.99 18-21% Plavix $147.12 17-22% Premarin $36.99 12-26% Xalatan $69.27 22-25% 1: Maryland Attorney General reported median price for a 30-day, brand name supply for three urban Baltimore ZIP codes 2: Range off the highest and lowest prices for seven discount cards. Source: Kaiser Family Foundation

"Excessive choice is confusing and probably accounts for the slowness of enrollment into this program," said Michael Hash, a researcher with Health Policy Alternatives, which did the study for the non-partisan Kaiser Family Foundation.

Researchers said Wednesday that there is no doubt the program benefits those who qualify for the $600 annual low-income subsidy from the government, but they also said that only 1 million of an estimated 7 million eligible low-income people have signed up.

For other consumers, the results are mixed.

Researchers chose seven cards at random, then compared their prices with retail prices published by Maryland regulators. They also created four hypothetical patients, each taking a different set of drugs, and compared prices. Their findings include:

• The cards offered 8% to 61% savings off retail prices, with savings varying based on the card, drug and pharmacy, for 10 commonly filled prescriptions.

• Prices for individual drugs varied widely between cards, with a difference of as much as a $142 a month for one of the patients.

• Mail-order drugs from Internet site Drugstore.com had prices comparable to mail-order prices available through the cards, many of which charge a $30 annual fee.

Researchers also noted some problems: With up to 43 different cards to choose from in some states, seniors are confused in trying to figure out which is the best. Direct comparisons between cards can be difficult, even for researchers.

The study is important because it is an independent look at a program that has faced critical reaction, from advocacy groups, who question the reported savings, and seniors.

Some patient advocates say interest in the cards may already have peaked, although Medicare chief Mark McClellan said Wednesday that about 25,000 members are enrolling each business day.

"We just canceled an informational forum for lack of interest," said Bonnie Burns of California Health Advocates, a non-profit consumer group. "A lot of (Medicare recipients ) have concluded that it's too complex, and there's not enough return."

Researchers said savings can be had, but seniors need to carefully compare cards. Medicare has responded by offering through its Web site and toll-free phone number a pared-down list of the five best cards by price and convenience based on ZIP code and drugs needed.