The world's premier drug regulator, the U.S. Food and Drug Administration, has an almost impossible job. Before a new drug can go on the market, the FDA must assess its safety, and its only guides are studies involving, at most, a few thousand people.

The job of monitoring safety doesn't end when drugs go on the market. But at that point, the FDA's toolbox for finding unexpected health risks is even sparser.

Fortunately, the world's premier drug regulator has a natural ally in the world's largest drug buyer: the federal government. The FDA said last week that it will begin using data from Medicare claims to look for unexpected health problems related to the use of prescription drugs. The new surveillance program is called the "Sentinel Initiative."

The amazing thing is that it's taken so long for the FDA and Medicare to begin working together to spot health hazards from prescription drugs.

Better late than never.

It just as easily could be called the "painfully obvious initiative," having been recommended for years by FDA staff and outside groups including the Institute of Medicine, part of the National Academies of Science. Whatever its name, the new collaboration is a huge step forward from the existing system, which depends on doctors and hospitals to report problems voluntarily.

By their very nature, medical complications and side effects that aren't spotted before a drug is approved are as difficult to find as the proverbial needle in a haystack. Problems sometimes become apparent only when researchers begin sifting through hundreds of thousands of patient records. Even then, it can be difficult to establish with certainty that any particular complication is related to a specific drug.

This month, for example, the Federal Aviation Administration prohibited pilots and air traffic controllers from using the anti-smoking drug Chantix. The agency cited potentially dangerous side effects that include heart attacks, seizures and psychiatric problems. The FDA had issued a warning about the drug in February, but the FAA's action was prompted by a report from a watchdog group called Institute for Safe Medication Practices.

Medicare claims data will make the job of spotting hazardous side effects a little easier. But its usefulness is limited because Medicare covers only senior citizens and the disabled, two groups that statistically are more likely to have multiple existing health problems. That makes it even more difficult to separate true complications from unrelated issues.

What's more, the new Medicare prescription drug benefit is administered by private insurance companies, so some of the important records aren't in the possession of the federal government. The FDA is working to add data from insurance companies' files, but, at least initially, the information won't be included. It should be.

The job of spotting potentially hazardous drugs could be made even more effective if the FDA could obtain data from the many other federally funded programs that provide prescription drugs. That means claims data for Medicaid, federal employees, the military and veterans receiving care at VA hospitals.

Of course, data are useful only if they're used. For decades, the FDA has been understaffed, its resources shrinking. That's expected to change over the next several years, thanks to the agency's many recent high-profile failures.

The FDA also should be given authority to require that drug makers study the effects of their products even after they've been approved for use. Drug makers often agree to do such post-approval studies, but then drag their feet gathering data. FDA records show that 62 percent of the studies promised for 2007 had not even been started by Sept. 30 of that year. During the same time in 2006, 63 percent of promised studies had not yet begun.

The FDA's Sentinel Initiative is long overdue. But it probably will be years before it bears fruit. In the meantime, Congress must ensure that the agency has the people, money and facilities needed to protect American consumers and, even more importantly, that the FDA use them aggressively.