Feedback on False Positives from Drug Testing, page 48

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 we do not give medical or legal advice.

Subj: Hair follicle tests
Date: 10/20/2008
About two and 1/2 months ago I went on vacation and forgot my migain med. My sister gave me about 10 or 12 tylenol 3. I had a migaine from flying and stess. I now have to take a hair follicle test for my job will I test positive for this. Thank You,

AskDocWeb: We’ve not seen any problems with those drugs on hair follicle tests, please let us know if you do have one.

Subj: Urine test
Date: 10/21/2008
My husband is currently taking 1200 mgs cacium, 200 mg plaquenil, and prednisone 10 mg something like take 10, 9, 8 and sos on till gone….he has discoid lupus and is scheduled for a urine test will there be a problem or should he ask his work to hold off on this test till his meds ease off?

AskDocWeb: It depends on what they test for, since Prednisone is a steroid, it may show up on a drug screen.

Subj: False reading for PCP
Date: 10/21/2008
I have recently been drug tested and I showed positive for PCP and TCA. Now I have accredited the TCA to my Rx of cyclobenzaprine but cannot find what has cause a false reading for PCP. I have never done PCP in my life! The other medications I am on are YAZ (birthcontrol) Nexium and Tylenol3. HELP!

AskDocWeb: The only drugs that have been reported to show up as a false positive for PCP are Diazepam, Ketamine, Diphenhydramine, and Effexor Tablets (venlafaxine hydrochloride), although Tylenol 3 may show positive for opiates.

Subj: Tested positive for Barbiturates
Date: 10/21/2008
Can Dilantin cause a false positive for Barbiturates??? I have tested positive for Barbiturates and have never taken anything like that. The nurse told me that Dilantin could cause a false positive and the wonderful quack doctor treated me like a drug head and he said no it WILL NOT cause a false positive. Please help me, I do not want to loose my chance for the job I am applying for. Thank you. Joseph

AskDocWeb: The references we have (3 and 20) say that Dilantin has shown up as false positives for Barbiturates on urine tests.

Subj: Ecstasy false positive
Date: 10/22/2008
Can Celexa or trazadone cause a ecstasy false positive. Also is there a list of what drugs will cause a false positive. I know that there are some psychotic drugs that can cause a false positive. Please provide the information if possible. Thanks A Million!!! For your assistance.

AskDocWeb: Yes, here is the list.

Subj: Tested positive for THC
Date: 10/22/2008
Hi I/m a dad with my son in rehab for drugs. He spent the weekend on a pass, and when returning to the recovery house tested positive for THC. He swears he never smoked, nor ate any pot. His explanation for the results of the test being positive could only be the hydroxy cut diet medication and some green tea, detox supliments, and hords of vitamins. Is it possible? Thanks,

Concerned Dad
AskDocWeb: The only one on the list of possible causes would be vitamin B2 and there is only a small chance of that.

Please note that there are health concerns with using Green Tea in some situations.

Subj: Testing positive for benzos
Date: 10/22/2008
I take 20mg of lexapro 1 daily, 300mg of wellbutrin 1 daily, 450mg of seroquel at night and 300mg of trazadone at night. I am testing positive for benzos and I do not do them. Are these medications causing this. Something is wrong. Please reply,

AskDocWeb: Sorry Kurt, the only one of those are on the list is wellbutrin but that hasn’t been reported for benzos, just amphetamines.

Subj: Toprol XL or Dyazide
Date: 10/23/2008
Can toprol xl or dyazide show up as false positive on a pre employment drug screen?


AskDocWeb: There are no reports of either drug causing any problems with drug screens.

Subj: What causes a false positive?
Date: 10/23/2008
I tested positive for methamphetamine after a grand mal seizure last year. I assumed it was due to the Provigil I was taking for Fibromyalgia fatigue. The doctors at the time said it couldn’t be the Provigil but when I was my GP he said it was the Fioricet I took for migraines. I assumed my medical records were adjusted but apparently not. I just had my first baby and now am being investigated by Social Services because of this, which I had forgotten about and didn’t even know was on my record! My baby cannot go home with me for several says until they prove he has no methamphetamine in his system. I was on so many prescribed meds at the time, trying to find what worked best for the Fibro but I cannot remember all of them. Effexore, Ambien, Fioricet, Provigil, Ativan, and then any OTC medicine as needed like Nyquil or something. And caffeine, of course. What causes a false positive like this?? Thanks.


AskDocWeb: False positives occur because of the chemical similarity of the various substances involved and the inability of the drug test to correctly identify the differences. Urine dug tests are not perfect. They do have an error rate but unfortunately in too many cases that error rate is ignored and the results are assumed to be accurate. If a confirmation test is not performed to show a false positive for what it really is then you are assumed to be guilty of drug abuse. And that confirmation test must be performed as soon as possible after the original drug screen, you can’t go back and change the record later.

Subj: Tested positive for Cocaine
Date: 10/23/2008
I am working in a transitional housing program and one of our tenants tested positive for Cocaine. He is currently on methadone and we are pretty sure that he did not use cocaine. Can a physical issue produce a positive?


AskDocWeb: Yes, if the individual was taking antibiotics for an infection, had kidney disease, or had diabetes, that may show up as cocaine on a urine drug screen.

Subj: False positive for Meth?
Date: 10/24/2008
I am a newly graduated RN working on a CD unit. One of my pts is on Benadryl. Can that cause a false positive for Meth use when reading a result on a UADL? Also can you recommend a medical book that specifically addresses the issues of how to treat pts. who are de-toxing? Thank you!


AskDocWeb: Sorry Adrienne, we are not familiar with what publications would be an aid in treating patients in detoxification. Benadryl (Diphenhydramine) has been reported to show up as false positives for Benzodiazepines, PCP, and Tricyclic Antidepressants 2-4 days after a single use. (Reference 45).

Subj: False positive for THC?
Date: 10/24/2008
Hi I have question. I am taking seroquel for sleep and lexapro. I was sick and was given amoxicillan. Can I get a false positive for THC? I would appreciate an answer because I am mandated to take drug testing and I am coming out with false positives. My freedom is on the line. Thanks,


AskDocWeb: Your antibiotic has been reported to cause a false positive for cocaine but not THC. The other two are not on the list.

Subj: Phenergan
Date: 10/24/2008
Can phenergan cause a false positive for barbiturates?


AskDocWeb: According to a Toxicology Lab Technical Brief from Dr. Joseph Graas, Phenergan-D has shown up as a false positive on drug screens.

Subj: Tested positive for cocaine
Date: 10/25/2008
Gentleman I recently tested positive for cocaine on an oral swab they claim that the tests are accurate and needless to say do not believe me. I’m am horrified that the possibility exists to test positive for a drug when in certain cases could cost you your job freedom and whatever else how can I prove it was amoxicillan and not cocaine?


AskDocWeb: The only we know of is to get a GC/MS confirmation test.

Subj: Prove I’m not guilty
Date: 10/27/2008
I read and printed out the information about false positives about drug tests. I just recently took a drug test and failed because of my medication, the medical revue company pretty much told me I’m out of luck. What can I do to prove that I’m not guilty. Thanks for listening.


AskDocWeb: If you get the GC/MS confirmation test then you put the burden of proof on them because it will show the difference between a false positive and a true positive.

Subj: Holy Basil
Date: 10/28/2008
I bought a dietary supplement called “Holy Basil.” It’s also called “Ocimum Sanctum.” It’s a basil that’s known to reduce stress and other benefits. Can this cause a false positive test. I want to be sure, as I can be tested at any time. Thanks.


AskDocWeb: We can’t be sure but there have been no reported problems with any kind of basil.

Subj: Oxycodone
Date: 10/28/2008
Can oxycodone give off a false pos for THC?


AskDocWeb: That is not likely, Oxycodone contains synthetic opiates but that is not similar, nor related to THC.

Subj: Energy pills?
Date: 10/28/2008
Can over the counter energy pills cause a false positive for barbital? I tested positive for it, they said it could be from prescription migraine medicine or anti-drepressants but I take neither so is there any way I could have tested positive because of that?


AskDocWeb: You will have to take a look at each ingredient in those energy pills to see if anything in them is on the list. So far, none have been reported to cause a false positive on a urine test.

Subj: Paroxetine or Alprazolam?
Date: 10/29/2008
Hi, Can Paroxetine hcl 80 mg a day and Alprazolam 1mg four times a day give a faults reading for cannabis. I got into an accident and tested positive for cannabis use and know have to go to court for DUI. Thanks,


AskDocWeb: There shouldn’t be any results for cannabis but Alprazolam contains benzodiazepines and is likely to show up.

Subj: Sustiva (Efanirenz)?
Date: 10/28/2008
Can Sustiva (Efanirenz) cause a false positive for THC in a hair sample? Thank you,


AskDocWeb: It appears that the potential for a false positive result only occurs with a urine test (CEDIA DAU Multi-level THC assay). If this occurs, ask the MRO to confirm the test results with a GC/MS confirmation test. Tell the MRO that you are on a medication that is documented to cause false positives. You do not need to reveal which medication you are taking. If necessary, offer to have your doctor write a confirmation letter, without naming the medication.

Subj: Prozac or Ultram?
Date: 10/30/2008
My daughter was given 2 prescriptions. One was for prozac(fluoextin) & ultram(tramadol). She tested positive for Benzos. Would these 2 medicines together make her test positive for Benzos? Can you let me know through my email at I need to find out about this as soon as possible. Thanks,


AskDocWeb: Sorry Trica, we post all replies so that everyone can benefit. Prozac has been reported to sometimes show up as a false positive for amphetamines (Ref: 31). There was also one unverified report that Ultram caused a false positive for PCP on a urine test.

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