WASHINGTON (AP) -- Eight advocacy groups asked a federal judge on Monday to ensure that no elderly or disabled Americans lose access to their prescription drugs as they enroll in the new Medicare drug plan.The groups filed the suit on behalf of about 6.4 million people who qualify for Medicare as well as Medicaid because of their incomes. Their earnings are usually well below the poverty level. Nearly 40 percent have dementia or other impairments.Medicaid, a state-federal partnership, now covers most of their prescription drug costs. But, beginning on January 1, Medicare will undertake that role.The advocacy groups are concerned that some of the "dual eligibles" will no longer be able to obtain drugs, either because they weren't enrolled in a drug plan or they could not understand communications about their new coverage.Even temporary glitches could be fatal for the beneficiaries, the groups contended in a lawsuit filed in the U.S. District Court for the Southern District of New York."If the government transitions 99 percent of these men and women flawlessly, there will still be 64,000 people without their medicine come January," said Robert Hayes, president of the Medicare Rights Centers, which is based in New York. "That cannot be allowed."The suit, which names Health and Human Services Secretary Mike Leavitt as the defendant, seeks a system under which existing coverage would be continued until these beneficiaries are enrolled in a plan that meets all their prescription needs.Under the current program, these people can choose any drug plan they believe meets their needs. If they don't choose a plan, they will be automatically enrolled effective January 1. Last month, Medicare sent letters to dual eligibles letting them know what plan they would be in if they didn't join one before December 31.Gary Karr, a spokesman for the Center for Medicare and Medicaid Services, said the agency has taken numerous steps to make sure that people with Medicare and Medicaid will have their drug coverage on January 1, including the automatic enrollments."We're also working on further steps to insure that, when a beneficiary goes to a pharmacy in 2006, they'll be able to get their prescription drugs, even if the only proof they have is that they are in Medicaid and Medicare," Karr said.Other parties joining the lawsuit were the New York Statewide Senior Action Council, The Coalition of Voluntary Mental Health Agencies, Inc., United Senior Action of Indiana, National Alliance for the Mentally Ill in Maine, Action Alliance of Senior Citizens of Greater Philadelphia, Massachusetts Senior Action Council and the Congress of California Seniors.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.