Theoretically, and Im not saying this is the case, but Tramadol can be adapted to. It stops being as powerful a sedative but remains an effective pain killer. Over time you can get the benefit with minimal drawback.
As for testing, plenty of people are cocky enough to think they can beat the test and evidence supports that belief. Lance Armstrong in cycling, MLB with steroids use (which drew Congressional interest) and even jockeys and owners doping horses in professional horseracing. They all think their method will either beat the test, or that the test simply doesn't target the drug or drug cocktail they're using.