About one in five teenagers have tried prescription painkillers such as Vicodin and OxyContin to get high, according to a study by the Partnership for a Drug-Free America. The 17th annual study on teen drug abuse, released Thursday, found that more teens had abused a prescription painkiller in 2004 than Ecstasy, cocaine, crack or LSD. One in 11 teens had abused over-the-counter products such as cough medicine, the study reported. It also found that the number of teens reporting marijuana use