I have never taken Methadone, ever. I am on Percoset for severe pain. The last 3 months they said I have not had any percoset in my system, but 3 months ago they said I had Methadone in my screening. What would cause the positive result for Methadone and a negative testing for Percoset when I take it every day? Please help, they are threatening to take my medication away from me because of being negative for the percoset. I am on Neurontin, effexor, pantraprazole, docusate, ferrous sulfate, prescription nasal spray, and trazadone, and Percoset.