For doctors or patients who notice side effect to a prescription drug (or a combination of several), there's one place to go: the FDA's Adverse Events Reporting System. This is where, once a drug is already on the market, the government can monitor side effects that for one reason or another did not turn up in trials.
The problem is that many patients aren't so forthcoming, and may not report -- to their doctors or the FDA -- minor side effects they notice.
But they will tell someone something: Google (or Bing or Yahoo).
According to a new study in the Journal of the American Medical Informatics Association, more than one in 250 people (0.43 percent) searched for one of the 100 best-selling drugs at some point in 2010. And if a whole bunch of those people searching for two of those drugs also search for, say, blurry vision, well, you might have just found out that that particular combination of drugs can cause hyperglycemia.