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Addiction and Substance Abuse

False positive for cocaine



I was a heavy crack cocaine addict, and have been clean since November 18th, 2005. I am in NA, have a sponsor, go to church, etc, am doing all the right things, and have NOT USED AT ALL since that time! I just got a new job a few days ago, and they wanted a UA done. I have not had to do that since I have been clean. The threshold was 300 mg/ml, and my result came up to 391!! How could that be??!! I have had a cold for the last week, and have been taking Theraflu and Dayquil PER INSTRUCTIONS! (no more than directions state!) Please help! I am so very frustrated. I have done so much work to put this all behind me, and here it is again! My employer told me that if I could show cause as to why it came up as a false positive, he would be very open to re-considering. (Although he will not re-test). THere has to be some explanation for this. Also, can you tell me what the range is or average mg/ml someone would show if they were actively using? Thanks for your prompt answer!


Sounds like a difficult situation.  The rates of "false positive" UDS for cocaine are quite variable, depending on the test used by the lab. 

1) The first thing to ask for is a "GC/MassSpec confirmatory test" to be done on the original specimen.  Most labs can easily do this.

2) It is rare for medications to give a false positive cocaine result ... common to give a false positive amphetamine result.  The lab can tell your employer which medications CAN give false positive results on their tests.

3) Your sponsor can talk with your employer about the strength of your program and the behavioral evidence that you have not relapsed.

Those are really your only options.  At least it sounds like the employer is willing to work with you on this ... perhaps suggesting weekly to twice monthly random screens for a few weeks would satisfy them? 

Good luck, and keep working on your program.  Long term sobriety rates are actually quite high with cocaine addiction ... even though short term relapses seem to be so very common!

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Response by:

Ted   Parran, MD Ted Parran, MD
Associate Professor of General Medical Sciences
School of Medicine
Case Western Reserve University