Philadelphia ? Kevin Costello stood before a small, mostly elderly group at the El-Shaddai Baptist Church in Philadelphia like a coach preparing for the big game.

The public-interest lawyer gave them pointers about the mountain of choices they would face in the new Medicare drug plan. They listened intently, and floated some polite questions.

But at the end of his 90-minute pep talk, Philadelphia police officer Ana Rodriguez, who’d come to the meeting for her parents, piped up: “It’s too much to swallow.”

For decades, senior citizens have longed for the federal Medicare program to cover outpatient prescription drugs. Now, the historic moment is near. Enrollment for the program’s greatest expansion will begin Tuesday. And early reviews have been less than enthusiastic.

Many people are bewildered, anxious and frustrated as they try to decide whether they should enroll in the new program.

The Medicare drug plan has been injected with a heavy dose of market competition. Beneficiaries, including some people with disabilities, can choose among dozens of plans with different premiums, co-pays and lists of approved drugs.

Those who forge ahead can become overwhelmed trying to make the right choice for their health and finances. Those who don’t could face penalties that would cost them a lot more in drug premiums in the future.

“We are driving our car into darkness,” said Costello, a staff attorney for Community Legal Services in Philadelphia. “There is going to be massive confusion.”

He fears that uncertainty will lead to the very problem that the new Medicare drug benefit is supposed to alleviate – namely, that some people won’t get the drugs they need.

When asked last month whether they planned to enroll in the Medicare drug plan, 37 percent of seniors said they won’t and 43 percent more said they didn’t yet know, according to a survey by the Kaiser Family Foundation and Harvard School of Public Health. Top reasons included: They already have an insurance plan. They don’t know enough about it. They think it won’t save them money. And it’s too complex.

“Confusion means some people are not going to do anything,” said Ross Schriftman, a Medicare specialist at Kistler Tiffany Benefits. “There are lots of choices and lots of moving parts to this.”

Although Tuesday will mark the start of the enrollment period, most people can apply until mid-May, when the program’s initial sign-up period ends. Coverage can begin on New Year’s Day.

The benefit will help fill a gap in drug coverage. Nearly half of Medicare recipients lack drug coverage at least part of the year, according to the Kaiser Family Foundation. And it promises to cap catastrophic drug costs for all beneficiaries.

“There is very good and comprehensive coverage,” said Medicare spokesman Gary Karr.

But the program isn’t cheap for taxpayers. The benefit will cost an estimated $37 billion next year and about $720 billion in the first decade, according to government data. U.S. Sen. John McCain, R-Ariz., called last month for a delay in the benefit’s launch to help rein in government spending.

“We are going to have a spending explosion set off on Jan. 1,” said Robert E. Moffit, director of the Center for Health Policy for the conservative Heritage Foundation.

He also said the benefit is jarring to seniors because of its “weird” design: Partial coverage for the first $2,250 in drug costs. No coverage for the next $2,850. And nearly full coverage for annual costs exceeding $5,100. “It is a product of a government committee; that’s why it looks so strange,” Moffit said.