WASHINGTON – Fighting the problem of fake drugs will require putting medications through a chain of custody like U.S. courts require for evidence in a trial, the Institute of Medicine reported Wednesday.

The call for a national drug tracking system comes a week after the Food and Drug Administration warned doctors, for the third time in about a year, that it discovered a counterfeit batch of the cancer drug Avastin that lacked the real tumor-killing ingredient.

Fake and substandard drugs have become an increasing concern as U.S. pharmaceutical companies move more of their manufacturing overseas. The risk made headlines in 2008 when U.S. patients died from a contaminated blood thinner imported from China.