Methadone - window of detection

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Methadone - window of detection

Post by hawkdoc » Wed Jun 02, 2010 4:29 pm

A donor submitted a specimen on 5/18 that was positive for methadone at a quantitative level of 16,290 ng/ml. EDDP was reported negative. We received a letter documenting treatment with methadone from 2/22-4/26.

The specimen was collected 3 weeks after the last dose of methadone was given. Would methadone still be present in a urine test after that much time esp. at that level? Also, does the fact that the EDDP was negative indicate acute/recent use?

I think I have to report as positive but want to make sure I have justification to do so. Am I correct in reporting as such?



Robert Swotinsky MD
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Re: Methadone - window of detection

Post by Robert Swotinsky MD » Wed Jun 02, 2010 10:16 pm

In general, a drug or metabolite is essentially (97%) gone in five half-lives. (Do the math.) The half-life of methadone is 15-60 hours (avg: 22 hrs). Thus, methadone should be essentially gone in 3 to 13 days (avg: 5 days) after last use. The 16,290 ng/mL concentration presented in this question is typical of therapeutic, current use of methadone, and is inconsistent with last use 3 weeks ago. I agree about calling this a positive result if the donor's use of methadone was limited to doses received and taken at the treatment center. But, if the donor was given a take-home supply of, or prescription for, methadone, then I would call it a negative result because the donor may have taken the take home/prescribed dose just before the test (and not 3 wks before).

EDDP has a longer half-life than methadone. The methadone-positive, EDDP-negative result may be more typical of urine collected immediately after last dose of methadone. Or, maybe the methadone assay had a low cutoff and the EDDP assay had a high cutoff.

Good question. As the question highlights, methadone was once best known as a treatment for heroin addicts, and is more recently becoming infamous as a dangerous (sometimes fatal) drug of abuse.


Re: Methadone - window of detection

Post by HHS-lab » Thu Jun 03, 2010 2:03 pm

It does seem odd that there was no EDDP found (or rather, the EDDP was negative as we are not sure what cut-off level the lab used or if there was some other reason they did not report the EDDP concentration) and the methadone concentration was positive at 16,290 ng/mL.

If the specimen in question is urine, one alternate explanation as to why methadone, but no methadone metabolite, was found is that the donor may have "spiked" the urine specimen with methadone by adding a small amount of his/her dose into the urine bottle and diverted the remainder for illegal resale. This is the reason why my laboratory switched from testing only methadone to the metabolite EDDP a few years ago as we were informed that methadone spiking and diversion was an issue with one of our client's demographic. However, I would assume that this is normally performed by the donor when they want to appear as if they are taking their prescribed dose (not once the treatment has been discontinued).

p.s. Thanks Dr. Swotinsky for this great Q&A forum. I have been following it for a few years and am happy to finally be a 'forum contributor' and not just a 'forum lurker'.

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