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Pharmacy/False Positives for PCP


Kim Howard wrote at 2007-09-05 01:05:39
I applied for a job w/ the county jail as a jailer. I took a drug test for them, which came back positive for PCP. I went the next day and took one at the hospital (the other was done at the jail) and it came back negative. I am on 200 mg of Lamictal and one claritin a day. Of course, I was never allowed to see the results of the drug test, I was also told that the results had been destroyed. Now that I have an attorney the results have resurfaced.   

All that I have been told is that PCP is what showed up. My dr was not even allowed to see the results so that he could look into this. I have never done illegal drugs in my life, but I have taken prescription drugs from the family dr and neurologist. So I believe that your urine can be switched. This happened after I told the nurse that Lamictal was for seizures.

Answer to your question, either your urine was switched or never tested correctly.

Sara wrote at 2007-09-06 13:44:26
PCP can and has come up postitive when people have taken too much cold medicine, or anything containing the cough supressant in it.

NUMBER4940 wrote at 2008-04-09 18:08:04
I've tested positive for PCP multiple times and was told that one of my medications is metabolized into it. (This I was told from different ER staff in different cities.) I've been on Tofranil and Thorazine at one point, and Lamictal at another.

Joawesome wrote at 2008-07-29 22:05:41
Today I tested positive for PCP because of my lamictal medications. Lamictal contains speed which is a type of PCP drug. If you are seeking employment for a job which requires a drug test, you need to show proof of your prescription for Lamictal. There is a law that will allow you to keep it private from your employer but the doctor or clinic that you test at must tell your employer you are fit to work despite your original test. Right now I'm waiting for my boss to call me back and tell me I can go to work again!

Logic wrote at 2008-12-11 14:09:11
Many things cause false positives for pcp. Some antidepressants, cough medications, cold medications, and asthma medications cause them.

There is about a dozen common medications which causes these false positives.  

Lisa wrote at 2009-03-30 12:07:28
Very interesting re: lamictal and positive PCP results.  My teenage son was admitted to the hospital, thru the ER for a severe seizure episode.  He takes 800 mg of lamictal, the non generic, every day.

In the course of the lab work, it comes back positive for PCP??!!!  We do not know what to think!?!?  We are having a more in depth blood test done, awaiting results.  

We are trying not to be naive parents, BUT... PCP???  Are there any other lamictal folks out there who have tested positive as well besides Joawesome and us??


PannyRose wrote at 2009-06-24 13:35:31
My 18 year old daighter was admitted to the ER last Wednesday, June 17. She was suffering extreme dizziness and nausea. It was terrifying to see. No test was spared (including a spinal tap - Ouch!). A urine sample cam back positive for PCP content. My daughter takes Lamictal, Neurontin and Frisium for seizures and Lo-Estrin for help with hormonal fluctuations. I have just read other patients accounts of the same situation, most likely due to the lamictal (brand, not Lamotrigine, generic). Everyone suspected my daughter of either trying narcotics or being a victim to someone slipping her some. I believe it is the Lamictal, also because the peak level came back at 27.4!!!

jaypath wrote at 2009-11-12 20:50:07
The above answer is incorrect. Just about every test will have false positives at some rate. This also depends on the specific laboratory testing method employed. Substances reported to cause false positive PCP include dextromethorphan, diphenhydramine, ibuprofen, imipramine, meperidine, mesoridazine, thioridazine, and venlafazine (or metabolites of these substances). In some cases, the level of these substances would have to be higher than therapeutic, meaning that the false positive would require "overdosing" on that medicine. A good source to find such inormation is on pubmed (, which is the government run index of research papers. For example, the above information was found using pubmed to locate a paper from 2002 (REFERENCE: Sena et al, False-Positive Phencyclidine Immunoassay Results Caused by Venlafaxine and O-Desmethylvenlafaxine, Clinical Chemistry 48:676-677, 2002).

eb wrote at 2010-02-17 17:07:36
Barb, not true, Effexor-venlafaxine comes up as false positive for pcp, also Benadryl can-diphenhydramine

Julie Budge wrote at 2010-04-09 01:26:05
Sorry Jaypath! Spoke to my psychiatrist about my own false positive for PCP. After phone calls and research he did discover that the break down of Lamictal, which I take, is almost identical to the structure of PCP and that is what causes it to show as a false positive. I have also found by reseach that both high doses of Cymbalta and Effexor will cause false positives.  

AliceN wrote at 2010-04-19 20:42:18
I am actually in the same situation. I am take I'm of Lamictal and am testing positive for PCP on at home tests. So, I have a feeling that this is possible because I'm in the same sit. I watched them test it 3x right after I gave them the urinanalysis.

CaramelKiss wrote at 2010-04-23 19:34:21
I am currently in dispute over my recent drug screening results after I was accepted for a new position. I took a urine test that tested positive for phencylidine. I was given the results immediately but the report stated "needed further testing".I had no idea what phencyclidine was until I called a nursing friend of mine and she informed me that it was PCP. I have been taking Lamictal for 5yrs now and have recently increased my dosage to 300mg/daily. My friend went online and found a site that stated that Lamictal does cause positive PCP results and that the lab has to use a maspectrometer to specifically test for PCP. I provided a copy of this article as well as a copy of my prescription from the pharmacy. It has been 3days and I'm still awaiting the final word for my new job.

Jake wrote at 2010-12-10 00:39:58
Same thing... 200mg / daily and I just tested positive for PCP as well. I'm not sure who's facial expression was better, mine or my boss. Funny now, but not when I was given the news!

Kara M wrote at 2011-01-25 19:01:00
I take lamictal and I have for years and I have NEVER taken PCP.. I'm not even 100% sure what it is! I'm now looking for a job and she tested me right there and it came back positive for PCP...I was stunned, very confused, and very angry since I don't really like being accused of doing drugs I've never done. I just had a second test done at an urgent care center that they sent away so hopefully that will clear my name!

Sober and Pissed wrote at 2012-06-08 05:43:25
I just found this site while searching for an explanation for my positive PCP test. I am a recovering addict, clean for three years now, and I REQUESTED that the md's do a drug screen because I missed a few days of work, and they do random tests. I didn't want to give them ANY room to suggest that I got high, especially when they know my past history. I have NEVER used PCP, and my test came back positive for it. Luckily, I was able to use my pho ne to look this up. I know I have a past that is questionable, but having been clean for three years, which is by no means an easy feat, I have FINALLY gained the trust of my family back. I've worked really hard, and I don't like it when people assume that I am picking up old habits when I'm not. The nurses knew that Lamictal would cause it, but the docs didn't? At least I was able to clear it up, so thank you to everyone who posted about this, it helped clear my name, at least my recent sober name.

My thoughts will be on my new associations, people who are not using, and who have found a new way of life. So long as I follow that way, I have nothing to fear. JUST FOR TODAY.

scaredteen wrote at 2012-06-28 22:20:38
I have recently gotten a new job and they required me to do a drug test. When I took my drug test it came back positive for PCP. The lady who did my drug test found it very strange that it showed up. She asked me if I was on any medication I had then told her that I have been on 100mg of Lamictal for the past 3 years. She didn't know much about this drug which then i had to explain to her what it was. Still not knowing much about it she sent it in to the lab to get it tested. They are letting me keep my job until the final test comes back (they feel like they have nothing to worry about.) Thank you all who have posted there stories on here i was very nervous (since i don't do drugs) Now I am a 100% sure Lamictal is whats doing it. I will find out next week whether i am right or not.

428roxy wrote at 2012-08-01 21:53:31
I just tested positive for PCP at the doctors' office and I also take Lamictal. How do I convince this doctor to believe that I have never touched this drug in my life? It was my first visit and now they think I do drugs. I am amazed because I have had drug test before that didn't show positive for PCP.  

fotogirl wrote at 2012-08-11 05:33:59
I was drug tested this past week and I came up positive for PCP and THC. I was a mess!! I work in a rehab and I am in recovery. There are different types of drug tests. Anyway they sent my sample to a lab and it was negative. I take Lamictal 50 mg and seroquel 25 mg. I was also sick and taking an antibiotic. I also took Aleve just before I went to work. So yes I believe that certain medications can test positive for PCP and THC.  I also know that there are different tests that are used and if read wrong which happens if the tester doesn't read the directions you can get fired for no reason. If you know you're drug free then fight it.

Carol wrote at 2012-09-11 16:33:51
I have been on Lamictal for years and tested positive for PCP.  The doctor said that is common.

Sha wrote at 2012-10-26 19:46:57
Research has shown that Lamictal shows false positivity for PCP, period.  As a physician I am performing conferences to educate other physicians about this. It is something to keep in mind when dealing with patients that are taking it. Lets not write patients off due to this, there are confirmatory test that can be done to rule this out

Concerned Mom wrote at 2012-11-25 12:30:06
My daughter who takes lamictal also tested positive for PCP.  I was happy to find this because we have had concerns about her using drugs, but this is the first time she tested positive for PCP and the first time she has been tested since being on Lamictal.  

BG wrote at 2013-04-21 03:42:08
I am currently in a Intensive Outpatient Program to help me overcome my addiction to opiates. I am required to take a drug screen test once a week. I also tested positive for PCP and I have never done PCP in my life. I am also prescribed Lamictal 100mg daily. There seems to be a large amount of people on Lamictal that are testing positive for PCP.  

Dorothy Smith wrote at 2014-11-07 14:40:55
I have taken lamictal for years and have taken drug screens for all my jobs (all in the psychiatric field) and NEVER tested positive for PCP. After taking their urine drug screen, all of a sudden, I tested positive for PCP. The employer, a psychiatric hospital, who was to hire me had asked all sorts of health questions prior to hiring ( which, by the way, is against the law). I was candid and stated I was being treated for depression and lamicatal was one of my prescribed medications. I was told, before the hiring could proceed, I would have to take a hair folical screen. I told them I did not use illicit drugs and took all my medications as prescribed.I had a urine drug screen done within 6 days of this mess and tested negative for all tested substances, including PCP. I believe this was their excuse for not hiring me. Now I am unemployed and looking for a new job.

Ronald wrote at 2015-09-04 14:54:28
I took my wife to a E R  and the E R Dr came out and said your wife tested positive for PC P and I said what is that and he said you know what it is . She was took by ambulance to another townhouse a better hospital and instead of doing another test they kept harking on the test from first Hospital. I told them at 2 Nd hospital I told them that she was tested every three months at a big Hospital that is up to date facility she has never tested positive PCP because they looked at meds knows what meds she takes Efexer and

Claratin and they can cause a fake positive but they would not listen  


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Barbara Judge


Outpatient pharmacy and general health. I have recently completed a Pharmceutical Care Certificate Program offered by Purdue University (Spring 1999 completion). I have personal experience dealing with terminally ill persons and their needs, as well as their families` needs. I graduated in 1984 from Pharmacy School and have been a Licensed Pharmacist since then. I have 18 years retail pharmacy experience. Prior to my pharmacy training I have 3 years hospital experience as a Nurse`s Aide.

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