COLUMBUS — A record number of Ohioans died from drug overdoses last year thanks in part to abuse of a synthetic painkiller far more powerful than heroin, the Department of Health said Thursday. The state said 2,482 people died from accidental overdoses in 2014, an 18 percent increase over the previous year and a reminder of the severity of a problem haunting the state for more than a decade. Abuse of the painkiller fentanyl, which is often combined with heroin or sometimes mistaken for it by addicts, is a significant contributor to the increase, the department said. Fentanyl was involved in 502 drug overdose deaths last year, up from 84 the previous year.