WASHINGTON - Tens of thousands of elderly poor people may have had trouble getting their medicine during the first two weeks of the government's prescription drug benefit, and about 20 states have been forced to step in to help them, the top Medicare official acknowledges.

The problems will be fixed, pledged Mark McClellan, administrator for the Centers for Medicare and Medicaid Services.

In some cases, people are not showing up in databases as being enrolled in a plan. When they do show up, many people are being told they need to pay hundreds of dollars before they can get their medicine. Instead, they should owe only nominal amounts.

“I'm working with the states, with the plans, with all of our partners to make sure people get the prescriptions they need,” McClellan said.

Under the program, about 42 million disabled and older people are eligible to enroll in private plans that will subsidize their prescription drug costs. Millions of prescriptions have been filled without trouble, McClellan said, but there is growing concern that some of the poorest beneficiaries cannot get their medicine.

Some advocacy groups say they believe McClellan underestimated the problems.

“We could see the problems coming. We expressed concern, and it was just pooh-poohed. Now, our worst fears have been realized,” said Jeanne Finberg, a lawyer with the National Senior Citizens Law Center, which is based in Oakland, Calif.

The problems go beyond technical difficulties, such as when computer databases fail to note that a beneficiary is enrolled in a plan. In some cases, private plans are just not following guidelines established for their participation.

The plans are not issuing emergency supplies as required and they have set up prohibited restrictions on the types of medicine that beneficiaries can get during the first weeks of the program, according to the American Psychiatric Association.

“Relapse, re-hospitalization and disruption of essential treatment are some of the consequences of the bureaucratic nightmare,” said the association's president, Steven S. Sharfstein. “I commend those states and other jurisdictions that have taken steps to assure that patients receive their medications in a timely manner.”

McClellan said he has directed plans providing drug coverage to make it easier for pharmacists to resolve questions about a beneficiary.

McClellan said plans were required to provide a 30-day supply of drugs, even if their plan does not cover a particular drug. In cases when a drug is not on the list, plans require pharmacists to get pre-authorization before dispensing the drug. Many plans are waiving the pre-authorization requirements, he said.

The agency also updated information on Friday so pharmacists can more quickly reach plans, McClellan said.

McClellan also said he contacted several governors and the staff of the National Governor's Association this past week on how best to help beneficiaries. Some lawmakers have demanded that the federal government reimburse states for those efforts, but McClellan said the insurers and other businesses offering coverage would do that.

“The plans are getting paid additional amounts to provide the extra coverage for the dual eligible beneficiaries. It's a matter of reconciliation,” he said. “If the state works with us ... we can send that information onto the plan so the plan reimburses the state for the difference.”

Democratic lawmakers wrote Health and Human Services Secretary Mike Leavitt on Friday with dozens of questions about the new program.

“We want to know why so many of our constituents have fallen through the cracks during implementation of the Medicare prescription drug benefit, and we urge you to take immediate action to correct the problems,” the lawmakers said.

A spokeswoman for Senate Majority Leader Bill Frist, R-Tenn., sounded a more optimistic note.

“We are pleased with the successes of the program and are working with (the Health and Human Services Department) to resolve the problems, which will naturally occur when implementing a program of this magnitude,” spokeswoman Amy Call. “But at the end of the day seniors will have better access to prescription drugs.”

McClellan said Medicare also has caseworkers on hand for beneficiaries or pharmacists who are having trouble navigating the new benefit. They can call 1-800-Medicare for help, he said.