Dealing with a Urine Drug Screen

Dr. Jana Burson

Drug screens are essential to detect ongoing drug use or relapse to drug use. It’s kind of like using X-rays to detect growth of cancer. The earlier it’s detected, the better.

Addiction is a disease that convinces its sufferers to lie so that the addiction can continue. In the end, drug screens help people recover from addiction, and are also important tools to measure the success of current treatment. When used in the right way, drug screening really does help patients.

Sometimes drug screens are wrong. The usual drug test is a quick and relatively cheap screen for the most commonly used drugs. If that screen is positive, but the patient denies drug use, a second test can be done that is very accurate, called a GC/MS (gas chromatograph/mass spectrophotometer) Because this second test is expensive, most clinics either ask the patient to pay for it, or run these tests only where the first test shows an unexpected result. Each lab hired to do a clinic’s drug screens has different screening tests, and use different reagents (chemicals) to do the test. False positives can occur, most often for benzodiazepines and amphetamines.Fortunately, cocaine and marijuana screens rarely turn out to be in error.

Working at an opioid treatment center, I get questions frequently from patients who are concerned about their positive urine drug tests. Overall, the tests are pretty good, but false positives can, and do, occur. Every different lab tests the urine samples with different reagents, or chemicals, so the doctor at your opioid treatment center should know what can cause a false positive at your particular lab.

Cocaine and Marijuana

First, a little about cocaine. The test for cocaine is very specific. The only thing that causes a positive for cocaine is cocaine. Despite similarities in the name, Novocain and lidocaine don’t cause a drug test to be positive for cocaine. No, it can’t be absorbed through the skin enough to give a positive, and if you are so close to cocaine that you’re handling it, I would say that counts as a positive anyway. Yes, it can be absorbed through mucosal lining – oral, vaginal, rectal – and again, that’s a true positive.

Benzodiazepines (Valium/Xanax)

Benzodiazepines are a different story. I’ve worked at clinics where diphenhydramine (Benadryl) causes false positive results. That is, the patient didn’t take benzos, but the diphenhydramine made their test positive, so it looked like they are using benzos.

I tell patients to avoid diphenhydramine, which can be difficult, since it’s in most of the over the counter sleep aids. But diphenhydramine does interact with the metabolism of methadone, and needs to be avoided.

I had a patient test positive repeatedly for benzos, and she swore she wasn’t taking them. I believed her, and had her gather all the medications she had at home, prescription and over the counter. When we looked at them, she had a bottle of some kind of herbal stress-relief medication. On a hunch I asked her to stop this pill. Within two weeks her urine drug screen was negative.

So what should you do if you get a positive drug screen and you know you have not used the drug in question? First, talk with the doctor about all of your prescription and over the counter medications. Your doctor should already know which drugs may cause false positives for that particular lab’s test chemicals. You may want to ask your clinic to do a GC/MS on the urine drug test in question.

Also, consider herbal/health food pills as a source for the positive screen. Dietary supplements do not undergo FDA approval before being marketed, and can be sold without any evidence of effectiveness or safety, so there’s little oversight of these products. Some studies discovered that dietary supplements can have ingredients not listed on the label. (1) In the case of athletes who must take drug tests, some supplements have been shown to contain banned substances.

I have a patient who repeatedly tested positive on drug screens for benzodiazepines, and the GC/MS showed Valium. This mystified her, and she said she didn’t take any benzodiazepines. Only after stopping a dietary supplement advertised to help with anxiety did her drug screen turn negative. I’m convinced this herbal remedy either contained a benzo, or a substance that caused a positive for benzos. There’s no FDA oversight with these herbal remedies, so the contents may or may not actually be what’s listed on the label.

So if you are testing positive for benzos, and know you haven’t taken any, consider stopping any herbal medicines that you are taking.

Methadone and Suboxone

Many patients who are prescribed methadone or buprenorphine (better known to some as Suboxone) are concerned about their employment drug screens. Because of the stigma attached to opioid addiction and its treatment with methadone or buprenorphine, patients don’t want their employers to know about these medications, and thus about their history of addiction.

Most companies who do urine drug screening hire a Medical Review Officer (MRO), who is a doctor specifically trained to interpret drug screen results. This doctor is a middle man between the employer and the employee, and though this doctor may ask for medical information, and information about valid prescriptions, this doctor usually can’t tell the employer this personal information. The MRO reports the screen as positive or negative, depending on information given to her.

Most employment urine drug screens check for opiates, meaning naturally-occurring substances from the opium poppy, like codeine and morphine. Man-made opioids like methadone, buprenorphine, and fentanyl, to name a few, won’t show as opiates on these drug screens.

A few employers do drug screening that specifically checks for hydrocodone or oxycodone. This is infrequent. It’s rare for employers to screen for methadone, and they almost never screen for buprenorphine, unless the patient is a healthcare professional being monitored by a licensing agency. The screen for buprenorphine is pricey, so the only doctors who tend to screen for it regularly are the ones prescribing buprenorphine. These doctors want to make sure their patients are taking, not selling, their medication.

Does your Employer Need to Know?

Patients ask if they should tell their employer they are on methadone or buprenorphine. In general, that’s probably a bad idea, unless it’s a special situation. So long as you can do your job safely, your medical problems aren’t any of your boss’s business.

CDL’s and Other Special Circumstances

The only exceptions to this are if you work in a “safety sensitive” job. This includes medical professionals, transit workers, pilots, and the like. These jobs may require disclosure of medical issues to protect public safety. For example, to get a commercial driver’s license (CDL), you have to be free from illnesses which may cause a sudden loss of consciousness behind the wheel.

The Dept. of Transportation still says that if you are taking methadone for the treatment of addiction, you can’t be granted a CDL. However, most of the studies done on methadone-maintained patients shows their reflexes are the same as a person not on methadone, so there’s no real scientific reason for the DOT’s decision. (1, 3, 4)



Patients can be impaired, and unable to drive safely, if they have just started on methadone, haven’t become accustomed to it, or are on too high a dose. These patients shouldn’t be behind the wheel until they are stable, even in a car, let alone an 18-wheeler. Methadone patients are likely be impaired and unable to drive if they abuse benzodiazepines. They shouldn’t drive any kind of vehicle. Ditto for alcohol. (2, 5)

Note:  At Denali Healthcare we rarely discharge patients on the result of a single drug test.  We use drug testing to monitor our patients and their care.  We do discontinue care and discharge patients based on a pattern of dishonesty, failing a drug test or using fake urine is simply a single element of dishonest behavior.  


1. Baewert A, Gombas W, Schindler S,, Influence of peak and trough levels of opioid maintenance therapy on driving aptitude, European Addiction Research 2007, 13(3),127-135. This study shows that methadone patients aren’t impaired at either peak or trough levels of methadone.

2. Bernard JP, Morland J et. al. Methadone and impairment in apprehended drivers. Addiction 2009; 104(3) 457-464. This is a study of 635 people who were apprehended for impaired driving who were found to have methadone in their system. Of the 635, only 10 had only methadone in their system. The degree of impairment didn’t correlate with methadone blood levels. Most people on methadone who had impaired driving were using more than just methadone.
3.Cheser G, Lemon J, Gomel M, Murphy G; Are the driving-related skills of clients in a methadone program affected by methadone? National Drug and Alcohol Research Centre, University of New South Wales, 30 Goodhope St., Paddington NSW 2010, Australia. This study compared results of skill performance tests and concluded that methadone clients aren’t impaired in their ability to perform complex tasks.
4.Dittert S, Naber D, Soyka M., Methadone substitution and ability to drive. Results of an experimental study. Nervenartz 1999; 70: 457-462. Patients on methadone substitution therapy did not show impaired driving ability.
5.Lenne MG, Dietze P, Rumbold GR, The effects of the opioid pharmacotherapies methadone, LAAM and buprenorphine, alone and in combination with alcohol on simulated driving. Drug Alcohol Dependence 2003; 72(3):271-278. This study found driving reaction times of patients on methadone and buprenorphine don’t differ significantly from non-medicated drivers; however, adding even a small amount of alcohol (.05%) did cause impairment.

Maughan RJ, Contamination of dietary supplements and positive drug tests in sports. Journal of Sports Science 2005; 23(9):883-9 About Drug Screens