Data from its 43 million Medicare patients to be used to track side effects of drugs

The Medicare program in the U.S. plans to use data from its 43 million patients in order to accelerate the detection of dangerous side effects from drugs already on the market.

Medicare administrator Mark McClellan says the aim is not just simply to learn more about the rates of rare but important side effects, but to also to get a better understanding who experience these side effects, to avoid using them in those patients.

McClellan says that in addition to spotting side effects, the Medicare database may be useful for determining which patients benefit most from a therapy and for also providing evidence about "off-label" uses that are widespread but not approved by the Food and Drug Administration (FDA).

He also says that with a vast new database of prescriptions and health outcomes, it can be determined quickly if certain drugs are associated with important complications in particular kinds of patients.

The federal health insurance for the elderly and disabled will start broad prescription drug coverage in January. The new benefits should help regulators investigate problems potentially caused by medicines.

It is unclear how many eligible patients will sign up for the Medicare drug coverage, but McClellan estimates 40 percent of all prescriptions in the U.S. will be covered by the program. Personal information will be removed from the database to protect patient privacy.

Various 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 reach the market. Millions of Americans took Vioxx before it was withdrawn from the market last September when a study showed the drug raised heart attack and stroke risk.

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

McClellan says the Centers for Medicare and Medicaid Services have limited ability to scour all the information but will rely on the FDA and other organizations for suggestions on how to prioritize its efforts.

The information will possibly be made available to manufacturers or independent researchers for analysis.