Having already struggled through the early confusion surrounding the Medicare Part D prescription drug program, some seniors are facing additional headaches this month because coverage for one or more of their medicines has been discontinued.

The potential problem arrived last weekend with the end of a three- month period for which insurers agreed to a Medicare requirement that they cover the drugs that plan participants were taking when they enrolled, even if those medications were not covered in the plan's normal offerings.

The so-called transitional period was designed to prevent any seniors from suddenly finding that any of the medicines they were taking were not covered. The participating insurance companies offering prescription drug coverage with Plan D originally proposed only a 30-day transition period, but federal authorities prevailed in mandating a 90-day period for transitional coverage.

The potential problems arising for seniors this month are twofold. First, the end of transition coverage comes as a surprise to many seniors. Second, the private insurance did not always do an adequate job of informing seniors enrolled in their plan of the change arriving in April.

Some seniors have been finding out this week when going to their pharmacy to refill prescriptions that coverage has ended. Others will get the news later. Whenever they learn of the end of transitional coverage, they are faced with paying for the drugs themselves — or pursuing one of several options.

The options for seniors who find a drug no longer covered are to shop for another insurance plan that does cover the drug now losing transitional coverage, petition their current plan to provide coverage, or ask their doctor to prescribe an alternative drug that their current plan does cover.

Regardless of the eventual outcome for participating seniors, the end of the transitional drug coverage period could mean trouble — or at least inconvenience — for many seniors, many of whom struggled in navigating through the confusing competitive insurance plans when they first signed up for Plan D coverage. The end of the transition period could also mean some headaches for doctors and pharmacists as they try to help their patients and customers.

According to senior Medicare officials, even after the 90-day transitional coverage ends, insurers are required to cover a drug until they make a formal ruling on a customer's appeal, or until the customer is able to have his or her doctor prescribe another drug that is covered. But that rule might not be widely known by seniors or their pharmacists.

Even though there appear to be safeguards in place to avoid leaving participating seniors without coverage, there will likely be some confusion. And, it is unclear whether the participating insurance plans will follow the requirements that federal Medicare officials claim are in place to avoid a senior being forced to pay out of his or her own pocket for temporarily covered drugs.

Providing three months of transitional drug coverage was helpful in reducing problems during the rollout of Plan D coverage for seniors. But it should have been more widely known from the beginning that certain drugs were only covered temporarily and that seniors would be faced with changing plans, petitioning their insurer or going back to their doctor for a different prescription.