WASHINGTON — A safeguard designed to ease elderly patients' transition into the Medicare drug program ended Friday, and that means some people will find they have to pay for their medicine out-of-pocket.

The government had told insurers they must cover a 90-day supply of a drug, even if that drug is not on the plan's list. As of Saturday, they won't have to.

During the past three months, plans were supposed to be notifying pharmacists and their customers when a prescription was being covered temporarily. However, it's not clear how often they have done so.

"I haven't had a single person come to me with notice from a plan warning them that a drug is transitional," said Buffie Sassvedra, director of New Mexico's State Health Insurance Program, which advises seniors about insurance coverage.

Some consumer groups worry that many elderly and disabled patients will try to get a prescription refilled, only to find that the drug is no longer covered. Some, they say, may not have the money to pay for their medicine.

Mark McClellan, the Bush administration's chief Medicare official, told reporters Friday that insurers must cover a drug until they rule on a customer's appeal, or until that customer switches to a comparable medicine.

McClellan said his agency, the Centers for Medicare and Medicaid Services, was prepared to fine insurers or to halt enrollment in plans that don't provide those services.

"We will be monitoring closely," McClellan said.

In a letter to President Bush, 10 Democratic senators said neither CMS nor the insurers have educated seniors about their options April 1. They asked the president to extend the transition period.