Doctors, hospitals and federal regulators are struggling to cope with an unprecedented surge in drug shortages in the United States that is endangering cancer patients, heart attack victims, accident survivors and a host of other ill people. A record 211 medications became scarce in 2010 — triple the number in 2006 — and at least 89 new shortages have been recorded through the end of March, putting the nation on track for far more scarcities. Some medical centers are rationing drugs — including one urgently needed by leukemia patients — postponing surgeries and other care, and scrambling for substitutes, often...