The box of prescription drugs had been forgotten in a back closet of a retail pharmacy for so long that some of the pills predated the 1969 moon landing. Most were 30 to 40 years past their expiration dates — possibly toxic, probably worthless. But to Lee Cantrell, who helps run the California Poison Control System, the cache was an opportunity to answer an enduring question about the actual shelf life of drugs: Could these drugs from the bell-bottom era still be potent? Cantrell called Roy Gerona, a University of California, San Francisco, researcher who specializes in analyzing chemicals. Gerona...