Urine drug testing, continued

Heroin tests positive for morphine. This is because heroin is metabolized first from diacetyl morphine, then to 6-monoacetyl morphine (known as 6-MAM) and then into morphine. Codeine is often seen in low levels in the urine drug screens of heroin users.

Heroin is morphine, except with two methyl groups attached. The two acetyl groups were put onto morphine to make it cross the blood-brain barrier more easily. Unlike the rest of the body, the space between capillaries in the brain is much tighter, preventing harmful material from leaking into the fluid that bathes the fragile brain. There’s also a basement membrane at the blood-brain junction, thicker than in other areas of the body. This blood- brain barrier keeps bacteria and large molecules of many drugs from getting access to the brain.

Acetyl groups apparently make it easier for morphine to cross, or be transported, through the  blood-brain barrier. With morphine, even if it’s injected, only five to ten percent of the drug crosses the blood brain barrier to reach the pleasure center, to produce the desired euphoria. However, with the addition of two methyl groups, creating heroin, around eighty to ninety percent of the drug gets across the blood- brain barrier. Thus with heroin, more drug gets to the pleasure centers of the brain. This is what makes most intravenous opioid addicts prefer heroin to injectable morphine, though personal preferences do vary.

On drug screens, we sometimes see 6-monoacetyl morphine (often called 6-MAM) as a metabolic product of heroin, and only of heroin. If this substance is seen in the urine, the person is using heroin, not morphine or other prescription opioids.  This molecule is difficult to detect, since it’s in the urine briefly, from thirty minutes to twelve hours after use.

Yes, poppy seeds can cause a low-level positive for opiates, because they contain tiny amounts of morphine. But unless you eat a mountain of poppy seed muffins, the cut-off for a morphine screening test is usually set high enough to prevent positives opiate tests from poppies. But if you were to decrease the lower limit of detection of morphine, positive tests could be seen in poppy seed eaters.

With heroin, the ratio of morphine to codeine found in the urine is much higher than 2 to 1, but with prescription morphine, this ratio is less than 2:1. Thus the ratio can give an idea whether the person taking a drug test has used prescription opioid medication or heroin.

Urine drug testing for benzodiazepines can also be confusing. On most EIA tests, the antibody in the test is targeted for diazepam (Valium). However, diazepam is metabolized into several compounds, including nordiazepam, temazepam (Restoril), and oxazepam (Serax). Patients who take only Valium as prescribed can be falsely accused of taking Restoril or Serax unless the person interpreting the test results knows this

Many EIA screens don’t test positive for clonazepam, so usually a special test must be added to detect this medication.

Other tidbits: the Z medications don’t cause benzodiazepine positive results on urine drug screen EIAs. False positives for buprenorphine can be seen in patients using codeine, naltrexone, or hydrocodone.

All of these finer points of drug testing illustrate the possible hazards of drug test interpretation. Companies doing drug tests on their employees shouldn’t try to interpret the tests by themselves. They should hire doctors specially trained to interpret these tests. This type of doctor is called an MRO, for Medical Review Officer. To be an MRO, the doctor must take an initial three-day course with about 22 hours of material, and then pass a two-hour written exam to become certified. The course and test must be repeated every five years to remain certified, since the science of drug screening can advance rapidly.

Companies usually contract with MROs to look at all positive tests, and to watch for problems that could affect the integrity of the test process. If a test is positive, the MRO contacts the urine donor, and asks questions about drug use and prescriptions in an effort to decide if there was unauthorized use of a medication or drug. Otherwise, many mistakes can be made and people can lose their jobs over an error in interpretation of the drug test. If the test is positive for a prescribed medication, the only report the employer should get is that the test didn’t show any illicit drugs. In this way, the MRO also acts as a buffer between employee and employer, safeguarding the health information of the employee.

Drug addiction treatment centers usually don’t need MROs, since they are not doing screening tests, but rather tests on patients know to have issues with addiction. At most addiction treatment facilities, the medical directors interpret drug testing results. Counselors shouldn’t be expected to interpret test results on their own, and should always be able to discuss unexpected results with the program physician.

18 responses to this post.

  1. Posted by dbc131832dr12a212aa212333DeF23417993312314 on June 15, 2012 at 1:22 am

    Screw drug tests. Lovely to have your permanent record of drug tests go to the insurance companies. They can use that at a later date against you, they always find a way. I KNOW they are needed, as you can’t trust what addicts say, BUT at the same time, I hope you trash the results after you take them (if you even accept insurance, most Suboxone doctors don’t, and most insurance companies don’t cover it anyway).


    • I am a mother trying to determine if my son is using illegal drugs after testing positive on a lab drug test for oxymorphone and marijuana. He claims he was using a pain killer but couldn’t produce a prescription to prove it. Some family seems to think he is using herion. Thank you for the helpful information. He denies using herion, of course. I am trying to make sure he is drug free for employment purposes and health. Also, he now has an infection in his liver, jaundiced in his eyes (diagnosed at the hospital.) Thank you for your helpful information.


  2. Posted by jason on October 22, 2013 at 7:28 pm

    I was told by my dr I tested positive for hydrocodone or oxycodone. I am 100% sure this is false. I am prescribed methadone (14 yrs) after breaking neck & back. Also prescribed gabapentin, very low dose of valium, & seroquel. Doc told me it was not the methadone causing false positive. I read last night seroquel also called quetiapine could cause this but who knows i am extremely confused. PLEASE HELP


  3. Posted by kris on December 11, 2013 at 8:15 pm

    question, if a person fails a drug screen for “opiates” and they do the gc/ms confirmatory test does the test only look for opiates or does it scan for everything again? i cant find this info anywhere!


  4. Posted by Ashley on January 26, 2014 at 7:34 pm

    My little brother is on probation and they do a lab UA. He just admitted to my mother and I he had been taking g oxycotin HCl 30mg and he has a perscription for percocet. Will both if these drugs come back the same (oxycondone)? Just wondering if we should be preparing him and yourself for him to go to jail.


  5. Posted by Ken on February 24, 2014 at 1:51 am

    I’ve been on hydrocodone and Soma for almost 4 years. Had a discectomy with fusion in my neck and also have deteriorating discs in my middle and lower back. I got a letter from my pain management doctor telling me our relationship was over because I had added water to my last urine test. When I arrived at the office the first thing I did was hit the restroom as I had been drinking coffee all morning. When I signed in I was told I needed to come back to give a sample. I mentioned I just went. They asked if I wanted a bottle of water and I said yes. I drank that 12 ounce bottle in about 5 minutes and then was able to give a sample about 10 minutes later. I completely filled the container and watched the technician seal it with a label and I initialed it.
    I am embaressed and also anxious as now I feel I will be blacklisted with pain doctors and made to look like a cheat. I also need the pain meds.
    I had a previous urine test come up negative for the hydrocodone. They asked if I was taking it as prescribed. I was but usually don’t need my first of three doses per day until late morning. This was the situation on this last test also. I had just taken a dose of hydrocodone when I arrived so when I gave the sample it had been about 15 minutes.

    Could drinking the water that and then urinating that quickly make the urine appear to have been diluted? The only other conclusion I can come up with is that they mixed my sample up with someone else’s .
    Any advice on how to get this doctor to listen to my story would be greatly appreciated. Reading between the lines I see that he thinks I am selling my pills.


    • Yes, drinking water quickly can give a dilute sample. The question is…how dilute? Labs test for urine specific gravity and/or urine creatinine levels, which indicate how dilute a urine sample is. There are cut offs beyond which it’s possible for the human kidney to dilute the urine. But over the last five years, scientists see that some people are able to dilute urine lower than originally thought.
      In the past, a urine creatinine below 20 was suspect, but small females with light muscle mass can dilute their urine creatinine down to 5-10 (I can’t remember the units of measure).
      I’m concerned that you aren’t being given a chance to meet with the doctor before being terminated from his care. This is a serious decision, and I think your doctor owes it to you to explain what the lab findings are. Labs are not perfect. For example, if you’re on a low-ish dose of hydrocodone, your doctor should call the testing lab and ask them to re-run your sample with no lower limit of detection, and I suspect it would be present, since you’re taking the medication.


  6. Posted by Darlene on June 4, 2014 at 2:07 am

    I have been researching this for a month and this is the closest I found for an answer. Can someone PLEASE help me figure this out?
    I noticed this paragraph:
    “Urine drug testing for benzodiazapines can also be confusing. On most EIA tests, the antibody on the test is targeted towards diazapam (Valium). However diazepam is metabolized into several compounds including nordiazepam, temazepam (Restoril) and oxazapam (Serax). Patients who only take Valium as prescribed can be falsely accused of taking Restoril and Serax unless the person Interpreting the test results knows this.”
    I take Xanax for an anxiety disorder, Norco and Soma for osteoarthritis, degenerative disc disorder and scoliosis, among many other illnesses. Back in March, I saw a new doctor at the practice who apparently thinks that everyone who takes Xanax is an addict, regardless of the fact that there is documented evidence showing 7 other medications didn’t work. He changed my prescription to Valium and took away my Xanax and Soma. Needless to say this did not work at all and my regular Dr changed it back when he returned 2 weeks later. During this time I was getting urine tests to make sure I was taking them. The first test came back negative for all so they gave me a second chance. The 2 test came back positive for Soma and neg for everything else, the third test came back positive for Norco and Soma but no Xanax. I was beyond frustrated and asked for a different lab which was declined. My fourth and final test came back positive for all of them PLUS Restoril and Serax was higher than the rest!! I never even heard of these 2! Now, my Dr decides she wants to believe this one and cuts my Xanax completely!!! I am shaking, heart palpitating basketcase and she still won’t give it back unless I can come up with an explanation. So.. If this can happen with Valium, can it happen with Xanax too? Please, I need answers as quickly as possible..


    • If the drug test you are referring to was taken within a week or two of your last dose of Valium, yes, it gets broken down into temazepam and oxazepam. It all hinges on the timing of the drugs test.


      • Posted by Darlene on June 5, 2014 at 10:02 pm

        It may actually have been 2-3 weeks prior that I was taking Valium and I may even taken 1 or 2 after that when my Soma ran out. I don’t understand your other reply though about the Xanax. You said it breaks down into four but, you listed 2 names.

      • Sorry, that’s the name of one of the compounds: “4-hydroxyalprazolam” and not that there are 4 breakdown products.
        It could be possible that Valium taken 2-3 weeks prior to that drug test was still causing positives for temazepam and oxazepam. Your doctor should consult the experts at the lab that does his testing.

    • Oh, and Xanax breaks down into 4-hydroxyalprazolam and alpha-hydroxyalprazolam only


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