More than 100 medicines now appear on the government’s drug shortage list. Those most often in short supply include anesthetics and oncological drugs, according to the Food & Drug Administration. Experts cite several reasons for the ongoing dearth of needed medicines. They include manufacturing and quality-control problems and ingredient import challenges. Generic drug industry consolidation has also contributed. FDA officials say drug companies are making significant investments to upgrade production facilities. But the ongoing shortages do not appear likely to end any time soon.