Urine Drug Testing

At April’s ASAM conference, I enjoyed an informative two-hour lecture on the finer points drug testing. Some of the information I knew, some I had forgotten, and some things I thought I knew, but I was wrong. Just goes to show me – again – I have to keep learning, because particularly in this field of medicine, things are always changing.

Dr. Peter Tenore, assistant professor at Albert Einstein College of Medicine, gave the two-hour presentation. He began with basic information about urine drug screening, and how to detect adulteration of a urine sample. Checking the urine creatinine and urine specific gravity are cheap and easy ways to see if a sample was adulterated. If the urine creatinine and/or urine specific gravity are below what is physically possible, it’s not human urine. These tests are fairly good, and detect most sample adulterations.

But besides these two methods, labs that do drug testing use ever more sophisticated ways to look for methods to thwart drug testing. These companies want to have good reputations. They want to be able to say they are savvy to the latest ways drug users try to cheat drug tests. These companies go to the same place drug users go for new ideas and technology – the internet. Testing companies buy the same products, advertised to beat drug tests, that the drug users do, in order to find ways to counter them. It’s a continuing game of cat-and-mouse.

Dr Tenore outlined the two types of tests done on samples to detect drugs. The first is cheap, quick, and fairly accurate, called the EIA, which stands for enzyme immunoassay. This test uses antibodies to identify the different classes of drugs. These tests are good for quick screening, but can have false positives. This mean a person has not used the drug, but the tests shows positive for the drug. In such a case, the same sample can be sent for more specific testing that won’t give a false positive, called GC/MS testing. This second test, more complex and more expensive, will show positive only if the drug really does exist in the sample. This second test meets the legal standard of beyond a reasonable doubt so if it’s positive…it’s positive.

Dr. Tenore took pains to remind us about the limits of drug testing, too. For example, oxycodone is a partially man-made molecule. The standard EIA (electroimmuno assay) tests for the morphine molecule, and oxycodone’s side chains, added to give it different opioid properties, often prevent the morphine antibody from attaching to the oxycodone molecule. In fact, if a patient prescribed only oxycodone is continually positive for opiates, oxycodone may not be the only opiate the patient is taking. Fortunately, there’s a specific EIA test for oxycodone, and most opioid treatment programs know to include this test, lest they miss important information.

I already knew that oxycodone doesn’t always show up as a positive for opiates, but surprisingly, many doctors who prescribe oxycodone don’t know this.

A few years ago, a patient being treated for chronic pain with oxycodone came for intake at the opioid treatment center where I worked at the time. His doctor, who prescribed oxycodone to treat a chronic pain condition, had just “fired” him. The patient was told only that there was a problem with his drug test. After talking with the patient, I didn’t feel he had the disease of addiction, and thus was not appropriate for admission to methadone maintenance at an opioid treatment center. This guy had never snorted pills, never used more than prescribed, never got extras from other doctors or off the street. He vehemently denied selling or giving away any of his oxycodone prescription, and said he took it as prescribed. This was puzzling.

I decided to call the testing lab, who said his sample was negative for opiates. I asked if the sample had been tested for oxycodone specifically, and was told “no.” Then with the patient’s permission, I called his pain management doctor, who was horrified at his mistake, and asked me to send the patient back to him immediately, which I did. Small errors like that can make big problems for patients.

The standard opiate EIA test works great for detecting drugs that get metabolized to morphine, such as heroin, codeine, and, of course, morphine. But special EIA screening tests must be done to detect the fully synthetic opioids like buprenorphine (Suboxone, Subutex), methadone, fentanyl, meperidine (Demerol), and tramadol. Other semi-synthetics are often negative for opiates on the standard EIA: oxycodone as described above, (name brands such as OxyContin, Roxicodone, Oxy IR, Percodan, and Percocet), hydromorphone (Dilaudid), and oxymorphone, (Opana). Hydrocodone usually does test positive on routine screening EIA.

Some drugs are metabolized into other drugs, which sometimes confuses doctors into thinking that two drugs have been used. For example, hydrocodone (Lortab, Vicodin) is metabolized into hydromorphone. So if I have a patient for whom I’m prescribing hydrocodone, I shouldn’t be surprised if, for some reason, I do a GC/MS test, and hydromorphone is also present. It does not mean the patient took Dilaudid. Similarly, oxycodone is metabolized to oxymorphone, and isn’t unexpected in the GC/MS of a patient prescribed Percocet.

In my next blog entry, I’ll explain how labs can tell whether a drug test is positive for opiates because the patient used heroin, or because the patient took prescribed medication.

11 responses to this post.

  1. Nice cartoon! Sure is nice to know that some don’t just admit for the sake of admittance. You cost the clinic money by not admitting the man to the program, but that’s not what is important.
    1) You saved the man from needless physical addiction to methadone.
    2) You probably clued in the clueless (other Doctor) and kept him/her from turning away more unwitting patients.
    Bravo Dr! So nice to see some keeping that oath. 🙂


  2. Posted by eve cruse on March 27, 2013 at 4:44 pm

    This article was helpful, however i am trying to find athe scale on which opiates are numbered. For example my urine test “scored” 128 on oxycodone and 164 on oxymorphone. I am prescribed 5 mg oxycodone for arthritis, degenerative disc and other back and pain issues. I also just found out i have cushings syndrome which is also causing some of the pain. I am prescribed 3 a day but honestly i at times take 2 cause 1 barely helps at all. Therefore last test i ran out ahead of time and only had 2 to take night before test. I am worried that dr will not prescribe for me anymore because of this so was hoping to see a scale to go by for these scores. I did call and talk to nurse about it todau and got appt to talk to dr tomorrow. I am so scared of the pain i will go thru if they stop my script. Thank u for listening. EVE


    • We can’t use urine drug levels to tell us what dose the patient is taking; the science just isn’t that precise. Most labs don’t correct for the degree of dilution, either. Plus, some opioids get metabolized to other opioids.


  3. Posted by Eileen on March 25, 2015 at 6:36 pm

    When having a gc/ms how long before your system is clean of percocet


  4. Posted by Judy Carter on April 27, 2016 at 1:30 am

    I have enjoyed reading your blog so very much. I need some honest and reliable information. I work in the field of Human Services with the developmentally disabled. I have worked with this population for almost twenty years. Long story short, I got my foot caught in a Hoyer Lift sling as I walked in front of a client in a wheelchair who utilized a Hoyer for transfers and my right knee was yanked and jerked violently when I had reached the slack limit of the sling loops. It was the worst event ever in my entire life. I worked at my two jobs for fifteen years, seven days a week. I did not report the accident when I fell, as there were quite a few of my co-workers taking a minor fall and then filing for workman’s compensation. While noble at the time, this course of action resulted in a total right knee arthroscopy in December of 2013, after a partial failed to resolve the issue successfully. My nature and mechanics of my specific fall resulted in extensive, complex, and degenerative tears of the entire medial and lateral meniscus and the presence of a 6 mm loose body. I have been diagnosed with DJD. I achieved 90 degree range and painless ambulation post-op, but the knee has slowly and steadily became stiff and very painful. Tradiional therapies such as NSAIDs are not indicated as I have Factor V Leiden and I am a lifetime Coumadin therapy patient. Early in my pain management, my anesthesiologist did not have me on a dose that was managing my pain. I work between 70-75 hours a week at a residence serving four developmentally disabled gentlemen with varying need levels. I applied a Fentanyl 25 mcg/hr. patch so that I could continue working at the pace that is/was required of me. I admitted my fault, and he understood. Twice subsequent to that, I have tested positive for morphine. I then tested compliant at a different laboratory with a different immunoassay ordered. He finally put me on Dilaudid 2 mg. q 8 hrs. PRN right knee pain. He increased me to 4 mg. q 6 hrs. PRN pain because I complained that I literally could not walk without significant pain, On my very last test before being released, I again tested positive for morphine. How could I have two false positives for morphine, a compliant test, and then another positive test for morphine with a different lab? I have NOT taken any morphine. Also, my career field would be considered “sensitive,” i.e., I have random drug testing there and I also had to complete detailed drug testing to secure employment with this agency. Does my physician have a poor understanding of the correct interpretation of UDT compliance testing, opioids and their urinary metabolites, and/or the metabolic pathways of the prescribed medication and what the possible urinary analytes might be based on the assay(s) ordered to confirm opioid therapy compliance? I am so very sorry for such a detailed letter, but I am hoping you can offer any advice. My physician gave me an emergent prescription for two 60 tablet courses of Dilaudid. I will take my last tablet tomorrow, and the medication has been taken exactly as prescribed. I have taken opioids for almost ten years and I am afraid of how I will react without that medication. He also gave me a prescription for 120 tablets of 50 mg. Tramadol. Thankfully, I have an appointment in 2 months at another pain management center. What would be my best course of action? Thank you in advance for your consideration.


    • well that’s weird. I know morphine can get metabolized to hydromorphone, in small amounts, but I don’t think it goes the opposite way. But you need more information – was this a screen or a more specific test called chromatography?
      Also, don’t forget that poppy seeds in food can cause a positive for morphine.
      I had a patient who tested positive for morphine, out of the blue, looked so shocked that I believed him. I ate the same poppy seed bagel as he described that night, and tested my own urine the next day and was positive for opiates. This was one of the rapid point-of-care tests, though.


  5. Do not waste anytime getting your drug addiction help because if you continue to use there is no telling what kind of consequence you will have to face but I can tell you this none of them will be to your liking.


  6. Posted by Jennifer on February 28, 2018 at 8:54 pm

    I take Naltrexone and I did a UA it showed up positive for oxy if that happens and I can test the UA they will send the urine sample off to spend it will that tell them whether it was Naltrexone or oxy


  7. Posted by Hana on March 2, 2018 at 4:51 pm

    99% of doctors wouldn’t have gone to the trouble you did to look into what had gone on with that patients test. Good for you for listening to and believing your patient and then following through and telling his previous clinician! Although I can’t say I’d want to go back to someone that made the error, it’s good to know there are people out there like you who take the time to look into things more deeply when something doesn’t seem right. Patients are in a very vulnerable position and pretty much at the mercy of doctors whether they get it right or not.


  8. Posted by Lexie on January 15, 2019 at 2:16 pm

    Amazing post. I personally use for most urine drug tests CLIA-waived cups, that are very economical and can detect most adulterated urine samples and up to 12 different drugs. I usually get them here, with great bulk discounts: https://www.helixdiagnostic.com/ It’s only for the most difficult cases that I pay for specialized tests.


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