false positive

[neilj]

I am 55 years old and tested positive for phencyclidine and i did not take this drug what might have caused this i have to explain to an mro tommorrow please help thanks neilio

[211katpost]

did you eat anthing with poppy seeds this can cause a false positive

[neilj]

Thanks for the info I wonder if robitussin has dextromethorphan in it because i did have a bad cold and took that, anyway i see the mro tommorrow and i guess i am screwed but i will check with an attorney about this because it is just not right to be accused of this. Anyway thanks for your help Neilio

[beanie485]

All these meds can cause False Positives some of them are over the counter medicines like ibuprofen

  Venlafaxine can cause false positives which is another medicine here is the website where you can look it up     http://www.clinchem.org/cgi/content/full/48/4/676

These can cause false positives as well  Nonsteroidal anti-inflammatory drugs, fluoroquinolones, and Vicks Inhaler are most frequently implicated
http://www.jfponline.com/Pages.asp?AID=4455

SUBSTANCE FALSELY IDENTIFIED ON TEST ACTUALSUBSTANCE TYPE OF STUDY NOTES
Amphetamine and methamphetamine Selegiline Single case report1,2 L-stereoisomer only detected (D-stereoisomer present in illicit drugs)
Amphetamine and methamphetamine Vicks Inhaler Several case reports, controlled-exposure studies1-3 L-stereoisomer only detected; most positives noted with twice recommended dosage
Barbiturate NSAIDs (ibuprofen, naproxen) Controlled-exposure study of 60 subjects (510 specimens)4 0.4% false-positive rate
Benzodiazepine Oxaprozin Controlled-exposure study of 12 patients (36 specimens)5 100% false-positive rate, some cases lack controls
Cannabinoid NSAIDs (ibuprofen, naproxen) Controlled-exposure study of 60 subjects (510 specimens)4 0.4% false-positive rate
Opiate Fluoroquinolone* Controlled-exposure studies (8 subjects) and case series (9 subjects)6 Most levels detected were below new 1998 threshold (2000 ng/mL)
Opiate Rifampin 3 case reports7
Phencyclidine Venlafaxine 1case report8 Confirmed by GC-MS (7200 mg intentionally ingested)
Phencyclidine Dextromethorphan 1case report9 (500 mg ingested)