The Medicare health plan will cover new Alzheimer's drugs after full U.S. approval for patients who participate in a health agency database, a move that expands on conditional coverage terms but companies have said that would limit use.

The registry requirement for the FDA-approved drugs applies to all Medicare patients, the U.S. Department of Health and Human Services' Centers for Medicare & Medicaid Services (CMS) said on Thursday.

Eisai Co Ltd and Biogen Inc's Leqembi received accelerated approval from the U.S. Food and Drug Administration in January and could receive full approval by early July.

Medicare, the government health plan for Americans 65 and over, currently pays for Leqembi only if patients are enrolled in a clinical trial.

The companies and patient advocates have been pushing for coverage of the drug without such a registry, saying the requirement would hinder use of the drug.

CMS said that to get Medicare coverage, people will need to be diagnosed with mild cognitive impairment or early dementia caused by Alzheimer's and have a qualified physician participating in a registry.

Eli Lilly is also developing an Alzheimer's drug that targets amyloid brain plaques, similar to Eisai and Biogen's Leqembi.