Hi, everybody. I’m new here, but wish I’d found this site a long time ago! I have a question that I have already sent to “Ask Cecil”-- I hope it’s not in bad form to ask it here in addition?
Anyway, here’s the question:
Has anyone ever shown up positive for cocaine on a drug screen, when they hadn’t done any cocaine, but had lidocaine in their system?
Everything written by, for, or related to the drug-testing industry says that lidocaine does not show up as a positive for cocaine because they’re chemically too different from each other, one being an “ester” (cocaine) and the other an “amide” (lidocaine).
OK, but these same papers also say that novocaine is structurally different from cocaine as well, and cannot cause a positive, even though (and they never mention this part) novocaine is also an “ester”. But all the medical literature that is NOT connected to the drug testing industry describes novocaine AS BEING structurally similar to cocaine. Though you would think that it either is or it isn’t, the definition seems to depend on whom you ask.
If novocaine IS chemically related to cocaine, why doesn’t the drug testing industry recognize this? Perhaps because they’d have to change all their documents??
And the second part of the question is: IF novocaine IS chemically related to cocaine due to both of them being “esters” and derivatives of para-amino benzoic acid, then wouldn’t it stand to reason that methylparaben, which is a preservative added to many injectable anaesthetic solutions such as lidocaine, could cause a positive for cocaine on a drug screen due to the fact that methylparaben is – and I quote – “a chemical similar in structure to paraminobenzoic acid”?
I wonder how many people have been labeled as cocaine users that were really only guilty of having novocaine or lidocaine used in a minor surgical procedure? I know it happened to me.
No. Cocaine assays test for cocaine as well as benzoylecgonine. These are not metabolites of lidocaine, despite the structural similarity between cocaine and lidocaine. Some dealers do cut cocaine with lidocaine, which explains when both chemicals are found using mass spec in hair samples, for example.
But don’t take my word for it.
Pap, MD.
I wasn’t referring to any similarity between cocaine and lidocaine, I know there isn’t any. I’m referring to a similarity between cocaine and novocaine (also known as procaine). And therefore a possible similarity between cocaine and methylparaben, which is often added to lidocaine. Thanks for the reply, though.
despite both being esters, cocaine and novocaine are no more chemically related than cocaine and lidocaine. from Dr. Paprika’s cite:
Methylparaben will not cause a false positive as benzoylecgonine is not a metabolite of it.
I may have spoken too soon there, as it appears there is some evidence that certain antibiotics can cause a false positive for cocaine. As this seems to directly contradict the previous cite, I wouldn’t take it as gospel, but I found a bunch of references to Tetracycline and Amoxacillin causing false positives.
Exactly, and Ampicillin is mentioned fairly often, too.
I think it’s Ampicillin and Amoxicillin that are officially recognized by the MROs as being medications that they will accept as causing cocaine false positives, as long as the patient has a legitmate prescription for one of them and can verify that.
Then the “positive” on he test is reported to the emp[loyer as a “negative”.
They can do this for antibiotics, but not novocaine?
Exactly, and Ampicillin is mentioned fairly often, too.
I think it’s Ampicillin and Amoxicillin that are officially recognized by the MROs as being medications that they will accept as causing cocaine false positives, as long as the patient has a legitmate prescription for one of them and can verify that.
Then the “positive” on he test is reported to the employer as a “negative”.
They can do this for antibiotics, but not novocaine?
I don’t see how amoxicillin or ampicillin could produce false positives, even in an immunoassay test; certainly a GC/MS shouldn’t confuse them. Nothing in the structure of either antibiotic has much in common with cocaine, which has a very distinctive tropane (8-azabicyclo[3.2.1]octane) functionality that should be easily distinguishable by GC/MS or even immunoassay.
Novocaine is structurally related more to benzocaine and lidocaine than to cocaine; it is simply the ester of para-aminobenzoic acid with N-diethylaminoethanol. It should be very easily distinguishable from cocaine by GC/MS.
The only reason I can think of that it might produce false positives in an immunoassay is that, since these two classes of structurally unrelated compounds both have the same therapeutic effect (local anesthetic), the tropane functionality in cocaine may not be the primary pharmacophore. The part of the molecule most important for binding to a receptor – and hence the part most likely to be important for binding to an antibody in an immunoassay – may actually be the ester/ether functionality and the alkylamino group. This would mean that benzocaine, lidocaine and novocaine might result in false positives in an immunoassay test. A GC/MS screen to detected cocaine and benzoylecognine would then be necessary to confirm the immunoassay result.
I’d agree with Roches. I can’t see how mass spec could confuse them, even if immunoassay did.
Many drug screening tests are not done by mass spec/GC. There are many different test instruments, and test kits available on the market. Most (all?) of these test kits are less acurate, but less expensive than MS/GC. They often have long lists of possible interfering substances.
labboy has it right - most drug testing is NOT done with mag spec/GC
Back when I was in the business we did very little with MS/GC because of the cost - maybe it’s gotten cheaper.
BTW, Roches, I am not aware of “immunoassay” tests for drugs - back when I was in the business it was all chemical analysis. Or maybe things have changed, or maybe I misunderstand the manner in which you use the term.
I want to emphasize that there is NOT just one “drug test”. There is a multitude of different tests. MS/GC is the most accurate (it can even identify a particular brand of a medication) but there are plenty of cheaper urine tests that are also considerably less accurate. The difference? About $5 bucks for “dipstick” tests with chemically treated paper strips, $25 for our standard urine test, $125 and up for MS/GC. When you’re testing 1200 addicts a week, some of them multiple times in that week, and you’re on a limited budget you’ll go first with the cheap-o tests and only use MS/GC for questionable or difficult cases, such as the gent we had with end-stage renal disaease where we had to use MS/GC to distinguish his legitimate medications from illegal ones.
For awhile, we’d use the cheap-o’s as an initial screen, and use MS/GC on the positives to confirm or deny them.
The truth is, it all depends on what the drug test is, and how it’s done. The cheaper ones WILL give more false positives - there was one that would give a positive for just about anything ending in “-caine”. Another would give a false-positive for PCP if you had taken Nyquil. We used to periodically swap one test for another, just so folks wouldn’t learn to game the system (addicts can be quite intelligent, even if some of their behavior is stupid).
So, the best defense is to 'fess up to anything you’ve had recently, OTC or prescribed, and hang onto your prescriptions for a bit.
I do get really irritated at the literature in the glossy brochures that claim no false positives. Unless you’re talking about MS/GC it’s weehocky - another demonstration that marketing and lying are not far apart, and in some cases identical.
Here’s the situation as I understand it –
Most labs today use a “cheapo” screen first, then use GC/MS to confirm or deny any positives that show up in the screen.
Enzyme Immunoassay (EIA) Multi-Panel screening is the most widely used method for initial screening, up to 95% of the time by some estimates, at least for employment-related testing. Many labs routinely follow up on any positive results from an EIA with a GC/MS test, since EIA screens are notorious for false positives (and false negatives too, for that matter).
My reason for asking about lidocaine and methylparaben was this:
I cut my finger at work, was sent to the clinic, given two shots of lidocaine to numb my hand, and then my cut was stitched.
AFTER that (two hours later) they collected a urine sample for testing. It came back “positive” for cocaine, the MRO said that lidocaine does not produce a false positive for cocaine, and I was fired.
I did some research, and by golly, the drug testing literature all does say exactly that – that lidocaine, benzocaine, and novocaine are all known NOT to cause false positives, even on EIA screens.
Hmmm… the problem is, I did not use any cocaine. I requested from the clinic the various documents related to the testing of my specimen, and got only a copy of the CCF I had signed at the clinic, and a copy of the “Results of Controlled Substance Test” that had been sent to my employer. I also got copies of the documents related to the treatment of my hand.
Now, the “Results of Controlled Substance Test” was a 1-page reporting of the test results of a 7 Panel drug screen – it says so right on it. Positive for cocaine, negative for each of the other substances included in the screen. No mention anywhere of any kind of confirmation test, GC/MS or otherwise.
So, I called the lab that the clinic had sent my sample to and asked a lady in the toxicology dept about confirmation testing, etc. She could not discuss my particular test results with me, as I did not order the test, but she gave me general information. Even though my employment was non-regulated, it was the policy of this lab to do a follow-up GC/MS on any positives, if the sample in question was accompanied by any CCF, before releasing the result.
I explained the situation so far to her, and she advised me to request the CCF form that the lab used from the time they recieved the sample, and also any and all documents related to the testing of my specimen (both tests) and their results. She advised me of what to look for in all these papers, such as specimen ID numbers not matching, breaks in the chain of custody, etc., and said she would definitely do the same thing if it were her, as labs do have occasional errors happen, no matter how hard they try to avoid them or how tight the control process is. She said I would have to request these things from the clinic, who would then request them from the lab, but that I had every legal right to obtain them this way and could not be refused.
So, I did just that – called and requested those very things, very clearly and individually, from the clinic.
I was told that “no other documents exist” and that I’d received “all that there is”. I was preparing to call an attorney when they called back a few minutes later. The lady asked me if I had received anything with the lab’s heading on it, I said no, only the papers from the clinic. The lady said she’d thought about it, and maybe I really didn’t have the documents I was requesting after all. DUH!! I was just now requesting that any papers be obtained from the lab, the others had been from the clinic itself.
She said she’d “get them in the mail to me” that very day.
I received (1) piece of paper in the mail from the clinic. It was a faxed copy of a “Requested Reprint” of – you guessed it! – a 7 Panel Urine Drug Screen, this time with the lab’s heading at the top instead of the clinic’s.
This one looked a little different – along with all the “negatives” on the list, it showed my “positive” as being for Cocaine Metabolite, rather than just simply “cocaine” like the other one.
This one also listed the “Cutoff Levels” for both the EIA and GC/MS testing. But just the cutoffs, no mention of any detected levels in MY sample, and no specific indication that a GC/MS had been done.
So, I am in the process of trying to find out if a GC/MS was ever, indeed, done. The clinic is stonewalling me on furnishing the documents I’ve asked for, saying that the GC/MS cutoff levels on the latest report are “proof” that a GC/MS was done. Baloney. That’s just proof of the cutoff levels, nothing else. I’m seriously thinking that the clinic has been charging employers for the cost of GC/MS confirmation, but not forwarding that part of the money to the lab and ordering GC/MS confirmation on the “positives”.
The lab doesn’t have to do confirmation testing on non-regulated samples such as mine, and even though it’s the lab’s policy to do so anyway, I’m sure it’s also their policy to do only what testing the sender pays for. They’re not going to do it for free.
But that would still leave the question, “what made the EIA screen test positive for cocaine”, if the lidocaine didn’t do it?
So I researched some more, including having the clinic read me the ingredients list off another bottle of the same lidocaine solution that had been injected into me. Methylparaben – never heard of it. Looked into it, and found all the stuff in my original post about it possibly being similar to cocaine in structure, as well as novocaine, etc.
So, my question was and still is:
Is it remotely possible that the methylparaben in the lidocaine could have caused the false-positive on the EIA? And, is it possible that novocaine may indeed cause the same thing on an EIA after all, even though it’s not “known” to?
“Known” and “does” are two different things.
If either of them “could” or “does”, it needs to become “known”.
Too many people could be getting fired over false positives due to these things on an EIA, if there is not a GC/MS follow-up.
GC/MS, of course, can tell one substance from another. But what about the employees whose determinations are made only on the results of an EIA?? Right now, the official line is that even EIA’s are not fooled by anything except antibiotics. If that is actually incorrect, someone needs to make it known.
Sorry about the length here, I get worked up about this.
Hijack-- (but it’s so unimportant I just couldn’t start a new thread). If one prepared it correctly, could one get a cocaine-like high by snorting Novocaine?
Legal Note-- I do not have access to Novocaine, nor do most people. I would think it easier to get one’s hands on Cocaine than Novocaine.
False positives can show up on any test – none are 100% accurate. Mass spec is a better test than a cheap assay. Cheap quickie tests are usually less senistive and specific than better ones. I agree either lidocaine or amoxicillin might show up on a bad test, but you could get a false positive with no other substance on board at all. Doing drug tests in methadone clinics, though, people often do lie about what they did take.
I can see where that would be a problem, people who have done an illicit drug trying to deny it. But there are legitmate prescription drugs and OTC medications that have made it to the list of “known substances” to cause false positives for illicit drug use, and are taken into consideration when a positive occurs (on the cheap screens only, not GC/MS). Different things are “known” to cause this for different drugs. How did these things get on the “known” list? Is there a process for calling a drug into question, so it can be evaluated scientifically and added to the “list” if it turns out to be a “causer” (for lack of a better word)?
Just an update on the fired-for-cocaine-positive story:
I just had a sample of my hair cut and analyzed by a certified lab, and the results were negative for any drugs in the last three months.
The day I cut my hand and gave a urine sample was about 5 weeks ago, so there’s no way that urine sample could have shown positive for cocaine using GC/MS. My hair was tested at Omega Labs, one of six in the country that do hair testing.
The clinic is still stonewalling on producing any documentation, so I have a lawyer now and he’s very optimistic. The clinic has a lot of explaining to do, at the least. Wish me luck.
Just an update on the fired-for-cocaine-positive story:
I just had a sample of my hair cut and analyzed by a certified lab, and the results were negative for any drugs in the last three months. That’s how far back the test goes.
The day I cut my hand and gave a urine sample was about 5 weeks ago, so there’s no way that urine sample could have shown positive for cocaine using GC/MS. My hair was tested at Omega Labs, one of six in the country that do hair testing.
The clinic is still stonewalling on producing any documentation, so I have a lawyer now and he’s very optimistic. My former employer has said that if I was able to prove I was innocent, I would be reinstated at my job. And the clinic has a lot of explaining to do, at the least. Wish me luck!
Oops, sorry about the double post.
I am not a drug user and rarely even drink alcohol but tested positive for cocaine in a hair drug test from my employer. So, to prove them wrong, I went to a different lab and paid for a hair drug test myself and it came up positive again. 3 months prior to the drug test I had been injected with Lidocaine several times for a biopsy. I had also had a tooth pulled and developed ‘dry socket’ and they gave me petroleum based Xylocaine to keep putting in the dry socket until it began to heal. However, I was told by 3 different doctors that Lidocaine will not show up as cocaine because they are not related in any way. I have been Google’ing and learning that there are ‘several’ none drug users that this is happening to. Too many people are losing jobs and reputations because of this. Is there anyone here who can help in any way? [Something] is obviously being missed.
Thank you.
The elimination half life of lidocaine is less than 2 hours. Even if you’d been injected with 1000 mg of lidocaine (an absurdly large amount), after 3 months (about 1000 half lives), the chances that there is a single molecule of lidocaine left in your body is less than one in 10^90. Even if they were specifically testing for lidocaine rather than cocaine, there’s no way it would have been detected.
–Mark