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Pharmacy/Urine testing for lidocaine


I am asking for help on a situation that I see has be a big issue on a lot of blogs.
I just got fired from my job of 10+ years due to a cocaine result. Since
2010 I have been on lidocaine and Vicodin daily. When I was going for random
Test I had told the drawer at the site that I was using Vicodin and had on 4 patches
(Yes I know that the prescrtion said 3 but it was a very bad couple of days.)
He said dont worry it would be ok.
About a week later I got a call from my central office say you came back with a positive
For cocaine. I work for the goverment who has a "0" tolerant for drugs and alcohol.
I spoke to the medical officer at the labs who said " there is not possable way lidocaine can
Bring a cocaine postive . My question is can the substance lidocaine bring a faults postive?
I really need help because if there are a reasonable doubt then I can fight this .  I do not use or abuse
Drugs . I am a person who has high blood pressure and is take diabetic medications .  So can you give me

Hi John,
I can give you my opinion but not the answer. In testing there is something called sensitivity and specificity. Sensitivity means how small an amount of the substance can one detet, while specificity means whether you pick up only the substance of interest or something similar too. In all instruments sensitivity and specificity are inversely related. Thosw which have high sensitivity will have low specificity and vice verse. I do not know what system was used to test, nor do I know the sensitivity and specificity of the instruments.
My opinion is that lidocaine can give a false positive for ocaine, under some circumstances.
Best wishes
Ravi Ghooi


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Dr. Ravindra Bhaskar Ghooi


I can provide information on drugs and medicines, their actions, uses, interactions and adverse effects. To avoid confusion, generic names of medicines may please be provided. I am a pharmacologist, having worked on animal and human pharmacology, and presently I am the Dean of Bilcare Research Academy, where we teach courses on clinical research. We dont work on saturdays and sundays, hence questions reachng me on these days will be replied on Monday, please bear with me.

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