The U.S. Medicare program will use data from its 43 million patients to aid quicker detection of dangerous side effects from medicines on the market, Administrator Mark McClellan said on Wednesday.

The federal health insurance for the elderly and disabled will start broad prescription drug coverage in January. The new benefits provide an opportunity to help regulators investigate problems potentially caused by medicines, McClellan said.

With a vast new database of prescriptions and health outcomes, “we can… determine much more quickly if certain drugs are associated with important complications in particular kinds of patients,” McClellan said during a speech to the Pharmaceutical Care Management Association.

It is not yet clear how many eligible patients will sign up for the Medicare drug coverage, but McClellan estimated that 40 percent of all prescriptions in the United States will be covered by the program.

Personal information will be removed from the database to protect patient privacy, he said.

“The goal isn’t simply to learn more about the rates of rare but important side effects. It’s also to get a better understanding of which kinds of patients experience these side effects, so that use of the drugs can be avoided in those patients, while targeting their use more effectively to patients who don’t have such side effects and may truly benefit,” he said.

In addition to spotting side effects, the Medicare database may be useful for determining which patients benefit most from a therapy and for providing more evidence about “off-label” uses that are widespread but not approved by the Food and Drug Administration, McClellan said.

A series of controversies involving prescription drugs such as Merck & Co. Inc.‘s painkiller Vioxx have prompted intense scrutiny of the way the government tracks the safety of medicines after they hit the market. Millions of Americans took Vioxx before it was pulled from the market last September when a study showed the drug raised Heart attack and Stroke risk.

Regulators now rely heavily on reports of serious problems from manufacturers or doctors to identify side effects that were not apparent before a drug’s approval. Experts estimate as little as 10 percent of potential side effects are reported.

The Centers for Medicare and Medicaid Services has limited ability to scour all the information it will gather but will rely on the FDA and other organizations for suggestions on how to prioritize its efforts, McClellan said.

The information also may be made available to manufacturers or independent researchers for analysis, he said.

The agency will ask for input on the plan a public meeting on June 14.