Four of five Standardbred trainers under investigation for illegally administering oxycodone to racehorses were exonerated when split samples showed no traces of the painkiller in urine taken from original samples that tested positive.According to the Washington, Pa., Observer-Reporter, Randy Bendis, Mickey Burke, Pat Medors, and Virgil Morgan Jr. were cleared because samples sent to Louisiana State University were found free of oxycodone, a substance commonly found in the prescription drug OxyContin.Each of the four trainers had one horse test positive for the drug in preliminary tests done by the Equine Toxicology Research Laboratory at West Chester University in early February. The samples were taken during routine post-race tests for winners and beaten favorites during a three-day span in late November, the newspaper reported.A fifth, unidentified trainer had a horse test positive after a race sometime in late January or early February. That split sample, tested by LSU, came back positive.Attorney Howard Taylor told the Observer-Reporter Morgan and Burke are considering legal action against the Pennsylvania State Harness Commission. Bendis was quoted as saying there is "a lot of incompetence in the whole procedure."Anton Leppler, executive secretary of the harness racing commission, defended the testing methods. He told the newspaper he regretted the preliminary results became public, but he said the fact the trainers were cleared before the commission took action proved the system is sound.