I am on chronic pain meds prescribed by my pain management doctor and I took my methadone 20mg and oxycodone ir 15mg at 0500 at 1pm the pain doctor did a urine drug screen and got results in office right away and I came up negative for the oxycodone ir and positive for my methadone now I am in trouble for coming up negative for the oxycodone ir even though I know I took it why did it come up negative and how can I prove I took it

Immunoassay (IA) testing (on-site) is notoriously inaccurate with an average error rate of about 20%. Seldom are these tests relied upon for other than preliminary screening. Confirmatory testing by Gas Chromatography/Mass Spectrometry (GC/MS) is required.

There are many other possibilities as this is a common occurrence in dealing with many classes of drugs that do not show up on standard opiate screens. It may be that the drug was below the level of detection for the specific IA. They are usually significantly higher than the LOD for confirmatory testing.

You should advise the testing physician, in writing, that the test results are in error. Keep a copy for yourself. Unless the urine sample was split, as it should be, and properly stored there is little you can do to disprove the results.

You have every right to challenge the results which places the testing agent(cy) in the position of proving their results. IAs do not hold up to challenge at any level. But first take the easy route. Adivse in writing and it may blow over.

More and more sage advice.