As seniors decide whether to buy into Medicare's new drug benefit, they may want to consider doing so by joining a Medicare Advantage plan.

Most of these plans not only combine and coordinate a beneficiary's entire package of Medicare benefits, but also add sweeteners such as enhanced drug coverage, vision and dental benefits, disease management programs, even transportation assistance. But like other forms of managed care, they may require members to use only doctors and hospitals in a defined network of providers, and they often impose restrictions on services that traditional Medicare does not.

In the Washington area, Aetna, Kaiser Permanente, Humana and Elder Health Mid-Atlantic offer managed care plans that include Medicare's new drug benefit while charging low or no monthly premiums; other choices have premiums as high as $163.

"I tell people to be very cautious and understand the rules of Medicare Advantage plans," said Howard Houghton, who counsels Fairfax County residents on Medicare options. He noted that people accustomed to going to any doctor they like may be unhappy with a plan that requires them to see a primary care physician before consulting a specialist.

The Washington Post asked HealthMetrix Research, of Columbus, Ohio, to compare the out-of-pocket costs -- including premiums and co-payments for office visits and prescriptions -- of several Medicare Advantage plans for three hypothetical beneficiaries -- one who was generally healthy and used few drugs, another who encountered a few health problems during the year and a third whose chronic illnesses required constant medication. (HealthMetrix studies health plans; its clients include Humana and Kaiser Permanente, but the company says it has not done research for Humana or Kaiser Medicare Advantage plans in the Washington area.)

Looking at five plans being sold in the Virginia suburbs, the analysis showed that a healthy person could pay as little as $380 in 2006 and as much as $1,236, with an average of $902. The moderate user of health care would spend $1,690 to $2,153, depending on which plan he had chosen; the average was $1,970. And the heavy user would have bills of $3,619 to $5,260, with an average payment of $4,655. The sole plan with no monthly premium -- Humana Gold Choice -- was not always the least expensive when all charges were tallied. Likewise, the plan with the highest premium -- Aetna's Golden Medicare Premier ($85) -- was never the most expensive.

Among Medicare Advantage plans available in the District and suburban Maryland, the Elder Health Choice plan had the lowest out-of-pocket costs under all three scenarios. A healthy beneficiary enrolled in that plan would pay about $654, compared with an average of $1,018 for other area plans. A chronically ill enrollee would pay $3,567 under Elder Health vs. $4,370 on average for other plans.

Elder Health has operated in Maryland for 10 years, offering a Medicare Advantage plan that enrolls a largely poor and frail elderly membership. But its entry into the District this year hasn't been completely smooth.

"They are running into all kinds of problems with their provider network," said Suzanne Jackson, director of the Health Insurance Counseling Project at George Washington University School of Law. Jackson said she's heard complaints that some Elder Health members are improperly getting billed from doctors who aren't listed on the plan's roster of preferred providers.

David Weinstein, president of Elder Health Mid-Atlantic Inc., acknowledged some problems with his company's expansion into the District. "It takes a while to develop relationships with providers -- it's one of those things," he said, adding that Elder Health also needs to educate older individuals about how the plan works.

"The bottom line is, if there is any issue that arises, [we] want to know about it," said Weinstein, who added that Elder Health contracts with two District hospitals, 100 primary care physician offices and 400 specialty doctor offices in D.C.

Seniors who may be best suited for Medicare Advantage plans include those familiar with managed care, perhaps recent retirees who have received care in similar plans.

"You'll be trading access to providers to get cheaper benefits," said John Gorman, who consults with managed care organizations. "Medicare Advantage is literally one-stop shopping . . . and many beneficiaries will find these plans to offer the best overall value if they can live with preferred networks of providers."

About 5 million -- 12 percent -- of Medicare's 42 million beneficiaries belong to Medicare Advantage plans, according to the Kaiser Family Foundation. The Department of Health and Human Services projects 30 percent of beneficiaries to be enrolled in Medicare Advantage by 2013. (The Congressional Budget Office foresees a rise to only 16 percent by that time.)

-- Christopher J. Gearon