Unprecedented shortages of injectable drugs have forced doctors to resort to medications that are less safe or postpone or cancel procedures, often at the last minute, according to the Food and Drug Administration and healthcare groups. Anesthesiology and oncology have been hit particularly hard. Last month, the only U.S. maker of Pentothal, used for 70 years to induce anesthesia, said it had abandoned plans to resume production, which it had halted a year and a half earlier. The painkiller morphine; amikacin, an antibiotic for serious bacterial infections; and carmustine, a chemotherapy drug, are among about 150 drugs in short supply. Hospital pharmacists and doctors report that patients have deteriorated or died because a drug wasn't available, says pharmacist Michael Cohen, president of the Institute for Safe Medication Practices. Others, he says, have been harmed by dosing errors stemming from drug substitutions.