Questions about False Positives in Drug Testing, page 251

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.

What drugs could cause a false positive test for morphine?


AskDocWeb: There are about 50 of them listed here.

Crystal meth or cocaine?
I recently smoked crystal meth them had a mouth swab about five days later. I tested positive for cocaine but have never used cocaine… Can I dispute this, being as I haven’t done what I failed for (cocaine). Or can meth appear as cocaine on mouth swab?


AskDocWeb: Sorry Sandy, this forum is for those who do NOT abuse drugs.

Anxious and upset
I have been an active sobriety member for over 6 years and am currently studying to work as an alcohol and drug specialist, and I am currently 29 weeks pregnant. I only take methadone, and my prenatal vitamin with once in a great while a tylenol or an advil for headaches. I keep coming up positive for PCP…..every single urine I have taken for my OBGYN has come up positive. I have never even seen PCP in my life. Wouldn’t know it if I saw it, and I spend all my time with my husband and 3 yr old son, so there’s no chance of being contaminated by friends or something. I’m a busy fulltime student and parent…my social circle is small. Very small.

I’m freaked out. Every test I have taken thru my methadone clinic has been negative. I have never given a positive drug screen since I first got clean years ago. What is going on with this? How can I prove that this is BS? They just did send the tests in for further testing somehwere….but Im afraid that whatever it is will come up positive still….I dont trust it. I am so anxious about it, and upset. Please help!


AskDocWeb: If you can find out whether or not their “additional testing” is a confirmation test, that may give you some peace of mind. A confirmation test would eliminate any false positives. Also check your meds to see if they contain diphenhydramine. For example, Tylenol Simply Sleeps contains diphenhydramine, which is known to sometimes show false positive for PCP on urine screens. Good luck and let us know how the additional testing turns out.

Positive for a drug that I have never taken
I recently had a drug screen at my pain mgt dr’s office that came back positive for a drug that I have never taken. I was postive for temazepam which is generic for Restoril a benzodiazepine that is in the same class as clonopin which I do take and have a prescription for. I am still trying to find out why the screen was positive for the other substance. I was treated very badly by some staff at the clinic and more or less called a liar. I did another urine screen for them. I am afraid the test is showing a false positive for the wrong medication. What do I do?


AskDocWeb: This happens more than you might think. We’ve had dozens of reports here about this happening, and then the pain doctor kicking the patient out of the program because of it. The problem is, so many people lie about their drug abuse that those working at clinics tend to think that everyone is lying.

The EMIT urine tests are known produce a certain percentage of false positives. You might demand getting a GC/MS confirmation test. If you request it they may want you to pay for it but if it means getting or not getting your pain meds it might be worth it.

Cetirizine HCl tablets
Hi! My patient is taking Cetirizine HCl tablets and wants to know if it could test positive for any other legal or illegal drug. Thank you


AskDocWeb: The only problem reported with Cetirizine HCl tablets is when it is combined with pseudoephedrine hydrochloride as in Zyrtec-D. Pseudoephedrine may cause a false positive for amphetamines (References: 3, 11, 18, and 21).

Positive for methamphetamine?
My husband had a drug test it came back positive for methamphetamine. He takes this medications riseridone-citalopram htdrobromide-diclofenac-temazepam-clonazepam -gabapentin-cetirizine hcl-phenytion dilantin novolin. would any of this have meth in it?


AskDocWeb: Hello Hilda, welcome to the forum. There are several dozen possible causes for a false positive for methamphetamine but none of your husband’s medications are on that list. Of course that doesn’t rule out the possibility of a false positive. To do that his sample needs to go through a GC/MS confirmation test. If methamphetamine is not in the sample the test result will come back negative.

I was prescribed robaxin 500 mg and I take drug screens twice a week, will it cause me to be positive for anything?


AskDocWeb: Robaxin is not known to cause any problems with urine drug testing for drugs of abuse.

Can methadone be absorbed through the skin?
Would like to know if you handle methadone with out gloves on can enough be absorbed though your skin to show up on a drug screen, i count out and put in containers that my uncle can use to take all his meds besides failing a screen i broke out in poxs i cannot take it breaks me out all over. Thanks for the help.


AskDocWeb: There has been some speculation about whether or not methadone could be used in a transdermal patch but it seems doubtful that enough would be absorbed through the skin to be effective. However, if you absorbed enough to cause a skin reaction then you probably have enough in your system to register on a drug test.

My counselor doesn’t believe me
Hi, I’m really upset today because I’m in drug rehab (voluntarily) and was told today that I tested positive last week for opiates and benzodiapines. I am positive that I haven’t taken any of these! I have been really working hard in rehab and am devastated by this’! I had one relapse and admitted it, even though it never came up on a test. The only medications that I have been taking any differently are some nighttime cold medicine for cough and a generic like Walgreens version if Benadryl during the day for allergies. Also I’m on prescriptions; Wellbutrin, Buspar, Resperidone and Trazadone, but I’ve been on them for awhile and haven’t come up positive. I’ve been racking my brain trying to think of what could’ve happened and am so worried that I will come up positive and be kicked out after doing so well for 7 months! I just need advice, I want my counselor to believe me, but I know she doesn’t.


AskDocWeb: In many cases the only thing that would convince the counselor that your test result was a false positive would a be a confirmation test that comes back negative. Several of the cold and cough meds, even the over-the-counter ones, are known to cause false positives for opiates. And, there are dozens of possible causes for a false positive for benzodiazepines. If you can get a GC/MS confirmation test, that should clear up any doubt.

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