False Positive For Methamphetamine Phenylephrine And Pseudoephedrine

I was told by my Dr. to take Claritin D (pseudoephedrine) and I already had been taking a nasal spray containing phenylephrine. I tested positive in a saliva test for ephedrine and methamphetamine. I have never taken methamphetamine in my life. Can these two compounds cause a false positive for methamphetamine?

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Ephedrine and pseudoephedrine (I'll use "ephedrine" to mean both from this point forward) can, and often do, show up as methamphetamine on a drug screen. The two compounds have nearly identical molecular structure, the only difference being a single oxygen molecule more (ephedrine) or less (methamphetamine).

The above notwithstanding, a drug screen can still differentiate the two but it takes a a certain kind of test called GC/MS (gas chromatography/mass spectrometry) — and the lab needs to be equipped to do it. But even a lab equipped to do GC/MS usually won't immediately go that route, because it's more complex and expensive than the usual starting point, which is called immunoassay.

The problem with immunoassay is that it's prone to false positives. It still makes sense to start with it though, because if that method yields a negative (i.e. good, for you) result, that result will have been obtained more quickly and easily (and cheaply) than with GC/MS.

Ideally, the analysis of a specimen should proceed like this:

-Start with immunoassay
-If it's negative (good, for you) it ends there
-If it's positive (bad, for you) resubmit the specimen for more thorough testing using GC/MS

That way both costs AND false positives are minimized.

The real problem (for you) occurs when a lab analyses your specimen using immunoassay, which yields a false positive for methamphetamine because of ephedrine use on your part, and you face consequences because of it despite not having used methamphetamine... do NOT let this happen to you! If you know you didn't use any methamphetamine but did use ephedrine, and the lab immunoassay yields a false positive for methamphetamine because of the ephedrine, AND they don't reanalyze the sample using GC/MS, you are being railroaded big time.

If it's your employer requesting the test and the lab they use doesn't even have the equipment to do GC/MS testing, it's up to them to have it sent elsewhere, or to change labs, or whatever... but the point is, YOU are a victim of their ignorance if this happens to you. Know how it works even if they don't, and don't let yourself be negatively affected by their ignorance: if you get a false positive for methamphetamine and they want to hold it against you, you need to find out how the analysis was done. If they did do GC/MS, you might be out of luck, but if all they did was immunoassay, you definitely don't need to just roll over and die.

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