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Dr. Bob is Robert Hsiung, MD,
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Posted by John Bostelman on September 8, 1998, at 8:20:36
A urine test was performed on someone with a long history of Benzodiazepine addiction. He claimed to be taking Zoloft but no Benzodiazapines. The test showed positive to Codeine and Doxylamine, but no evidence of Zoloft or Benzodiazapine.
The logical conclusion is sample switching, however, could this result be suggestive of deliberate masking? If so, what is the likely interraction,
to create the masking effect?
Posted by Toby on September 11, 1998, at 12:49:04
In reply to Masking of Benzodiazepines in Urine testing, posted by John Bostelman on September 8, 1998, at 8:20:36
What kind of drug test was used? Thin layer chromatography is relatively insensitive and detects only high levels of a selected group of drugs, giving frequent "false negatives." You need to contact the lab and find out what test they are using and what the sensitvity is and also whether you need to request certain tests specifically in order to get them to do the more specific tests like EIA, FPIA and RIA. Codeine is not likely to mask benzodiazepine use since they show up in different places on the Chromatograph. Perhaps the patient is substituting one for the other. Codeine can be detected 1-2 days after last use, while benzos can be detected up to a week after last use depending on which benzo was used. Repeat UDS is probably needed here.
This is the end of the thread.
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