WASHINGTON — Medicare said Thursday it’s considering a cut in enrollee premiums, after officials stuck with an earlier decision to sharply limit coverage for a pricey new Alzheimer’s drug projected to drive up program costs.

The agency “is looking at that, and is still going through the process,” spokeswoman Beth Lynk said of a potential reduction in premiums, as Medicare announced its final coverage decision for Aduhelm, a drug whose benefits have been widely questioned in the medical community.

Officials said Medicare will keep coverage restrictions imposed earlier on the $28,000-a-year medication, paying for Aduhelm only when it’s used in clinical trials approved by the Food and Drug Administration or the National Institutes of Health.

The projected cost of Aduhelm was a major driver behind a $22 increase in Medicare’s Part B premium this year, boosting it to $170.10 a month. That price hike is already being paid by more than 56 million Medicare recipients signed up for the program’s outpatient coverage benefit. Lawmakers have called for a rollback and Health and Human Services Secretary Xavier Becerra already directed Medicare to reassess.

Thursday’s coverage decision illustrates the impact that a single medication can have on the budgets of individuals and taxpayers. It comes as legislation to authorize Medicare to negotiate prescription drug prices remains stuck in the Senate, part of President Joe Biden’s stalled social and climate agenda.

That’s left Democrats with nothing to show on their midterm election-year promises to cut prescription drug costs, unless they can overcome internal disagreements. Most Medicare recipients have their premiums deducted from their monthly Social Security checks. And despite a big cost-of-living increase, they’re feeling the bite of inflation.

Medicare’s determination on Aduhelm included an important caveat. Officials said that if it or any other similar drug in its class were to receive what’s called “traditional” FDA approval, then Medicare would open up broader coverage for patients. Such approval is granted when a medication shows a clear clinical benefit.

That was not the case with Aduhelm. It received what’s known as “accelerated” approval last year because of its potential promise. But manufacturer Biogen is required to conduct a follow-up study to definitively answer whether Aduhelm truly slows the progression of Alzheimer’s. If that study is successful, FDA would grant full approval.

That would also open up Medicare coverage.

Dr. Lee Fleisher, chief medical officer of the Centers for Medicare & Medicaid Services, said “there will be quick access for Medicare beneficiaries” for Alzheimer’s drugs that receive the traditional FDA approval, after demonstrating a clear benefit.