Questions about False Positives in Drug Testing, page 291

False Positives Forum

This forum is intended to help those who Do NOT Abuse Drugs. We do NOT support the illegal use of any substance. If you have experience with false positives, share your experience. What would you tell someone about drug testing and false positives? Please remember that this forum is not for medical or legal advice. For that you need to consult with Ada Doctor or an Attorney.

Positive for PCP?
Date: 5/31/2006
I tested positive for pcp which I have no clue what it is so never taken it. I take Effexor, Wellbutrin and imatrex. I have read that the Effexor can cause a false positive for pcp????


AskDocWeb: Yes, according to the Blue Grass Drug Screen company Effexor (venlafaxine hydrochloride) may test false positive for PCP (Reference: 52). Their iCup testing device is used by:

  • Military – Drug testing
  • Manufacturers – Pre-employment drug test, random drug test, and post accident drug testing.
  • Businesses – Drug Free Workplace programs
  • Occupational Medical Facilities
  • Drug treatment facilities and Rehabilitation
  • Probation and Parole drug testing
  • Correctional Facility drug testing
  • High Schools – High school athletes

Urine tests that show false positive for PCP are eliminated when the original sample is sent to an outside lab for confirmation testing.

False positives for k2?
Date: 6/1/2006
I recently tested positive for k2 and I have been clean for 6months and am involved in drug court I know it is due to smoking e-cigarette do you know if this can happen I heard that it is true I just need more answers to prove my innocents!! My kids were taken because of this (e-cigarette) and it is very serious that I know everything there is to know about e-cigarettes and false positives for k2.


AskDocWeb: Sorry Lynne, our database currently has no listing for anything that might show up as a false positive for K2. Have you requested a confirmation test?

Need proof!
Date: 6/3/2006
My friend has recently taken both urine and hair test and came up positive for cocaine. She doesn’t use the drug. The hair sample showed that she had been using for the last three years and oddly enough that is when she started taking her vyvanse. On the screens she showed negative for everything else, I know it can show up as meth, so why the positive for cocaine and negative on meth. This is very important to me because she is going to lose her kids if we can’t prove the false negative. Is there anything I can do?


AskDocWeb: We could be wrong but it sounds like you need to make a distinction between false positive and false negative. With false negative the drug that is expected to be in her sample is not found. That means that she is not taking her medication. A false positive is a false indication that a drug is in the sample when it is not really there.

Vyvanse is a prodrug for the chemical dextroamphetamine and may test positive for amphetamines. On some cheap urine tests it can show up as meth.

Here’s the bottom line: The only way to prove that the original test was a false positive is to get additional testing done on the original sample. It is preferable to use a certified independent laboratory for a GC/MS confirmation test. Good luck!

Pre-employment drug test?
Date: 6/3/2006
I am taking acyclovir for coldsores… will this show up on ANY DRUG SCREEN? I needed it bc stress caused sever cold sores, but now im worried i will fail a pre employment drug test… help…..


AskDocWeb: Acyclovir is not known to show up on any kind of drug test that tests for drugs of abuse. However, it is always possible to get a false positive test result so be sure to disclose all prescriptions and over-the-counter remedies you are taking.

Date: 6/4/2006
Can fastin give you a false positive drug test?


AskDocWeb: Fastin contains alkaloids from the plant acacia rigidula. This plant is commonly known as blackbrush, which grows mainly in Texas. In 1997 and 1998, two scientific papers were published by researchers at Texas A & M University describing properties of the plant and its effects on cattle. The researchers found trace amounts of amphetamines in the acacia rigidula. It is not clear if the manufacturer takes steps to remove those trace amounts of amphetamines or not so it is possible to test positive for amphetamines.

What will test false positive for methamphetamines?
Date: 6/4/2006
What would make a false positive for methanphetemines? My girlfriend came up positive for this and she doesnt do meth. how ever she does have one kidney and she takes bactrium and sometimes takes valatern 75mg n ibuprophen, tylenol sometimes. Oh and she takes blood pressure pills.. but i know that drug tests can have issues. so does neone know what can cause a false positive so I can tell her what to stay away from so she wont have to worry about this?


AskDocWeb: There is a long list of substances that might cause a false positive on urine drug tests. Anyone subject to drug testing should read through that list at least once.

Sulfamethoxazole and trimethoprim?
Date: 6/5/2006
Can sulfamethoxazole and trimethoprim cause u to have a positive drug test for benzodiazepine?


AskDocWeb: Neither of those antibiotics are known to cause a false positive for anything on urine drug tests for drugs of abuse.

Inhalers and LC/MS analysis
Date: 6/5/2006
Is there a possibility that a combination of Strattera, albuterol inhaler and dulera inhaler use could create a false positive test for amphetamines using a LC/MS analysis?


AskDocWeb: To our knowledge no, the LC/MS would be able to tell the difference.

Chromatography test
Date: 6/5/2006
I have been suffering from intractable migraines since 1996. I was taking methadone for chronic pain since 2001, I think. Last summer, 2012, I weened myself off methadone since it was not working. I was completely off in August and turned in what I had left except for what I forgot was in my purse, which I turned in the next month, Sept. I also have been taking cetirizine hcl for several years.
Since September, ALL my chromotography urine tests had been coming back positive for methadone until March. When a certain tree was blooming I started getting sinus headaches which I have not had in years. The pharmacist told me to stop the cetirizine hcl for 7-10 days then start back. It worked. However, I had a pain clinic appointment around day 6 or 7 of being off the cetirizine hcl. That test came back negative for methadone. All tests since then have come back positive. I feel so much better since off methadone and have taken any since Aug.

It is now June. The pain clinic overlooked the positive results until that one test came back negative. Now they refuse to give me any hydrocodone. Hydrocodone and Imitrex are the only things that work for my migraines. Is there any way cetirizine hcl can show a false positive for methadone in a chromotography test? The pain doctor and my primary doctor’s nurse practitioner says there is no other test. I understand their position that even if they believe me, the paper work says otherwise. Please, what can I do to find out what is going wrong? Thank you.


AskDocWeb: The chromatography test is about as accurate as you can get. Of course the quality of the lab doing the test may ba a factor. Was the laboratory that did the testing a SAMHSA certified lab? SAMHSA refers to the Substance Abuse and Mental Health Services Administration, a branch of the U.S. Department of Health and Human Services. For a list of SAMHSA certified laboratories see page 185.

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