Joe asked
I failed a urine drug test because it said I tested positive for a benzo and I don't take benzos. What could be the cause?
Answer
There are multiple medications that are known to cause "false positives" for "benzos", also known as benzodiazepines. Common benzodiazepines include:
- Xanax (Alprazolam)
- Librium (Chlordiazepoxide)
- Onfi (Clobazam)
- Klonopin (Clonazepam)
- Tranxene (Clorazepate)
- Valium (Diazepam)
- Prosom (Estazolam)
- Dalmane (Flurazepam)
- Ativan (Lorazepam)
- Versed (Midazolam)
- Serax (Oxazepam)
- Restoril (Temazepam)
- Halcion (Triazolam)
Depending on the type of test you took (most likely a urine based immunoassay), false-positives are relatively common, which unfortunately can have significant consequences when it comes to employment and things of that nature. Below, we discuss false-positives for benzodiazepines and potential solutions.
What Causes False-Positives For Benzos?
Most common drug screenings are urine-based "immunoassay" tests. Immunoassays are subject to false positives.
These tests work by utilizing antibodies to react to a specific drug compound (e.g. diazepam). When the specified drug is present in a urine sample, an antibody binds to it, producing a reaction that will be recorded as a "positive" result. Unfortunately, these tests have a significant problem with 'cross-reactivity'. Compounds that are not being tested for occasionally react with the wrong antibody (i.e. 'cross-react') which will also get recorded as a positive result, even though it is a false-positive. Most immunoassay tests can't discern between reactions, so any reaction will get recorded simply as a positive result.
There are many drugs that have been reported to cause a "false-positive" for benzodiazepines. These include:
- Zoloft (Sertraline)
- NSAIDs (Non-steroidal anti-inflammatory drugs) like naproxen and oxaprozin
- Seroquel (Quetiapine)
In terms of NSAIDs, oxaprozin has a fairly large body of evidence that it can cause false positives for benzos. In fact, the prescribing information for the drug warns about potential false-positives:
"False-positive urine immunoassay screening tests for benzodiazepines have been reported in patients taking DAYPRO [oxaprozin]. This is due to lack of specificity of the screening tests. False-positive test results may be expected for several days following discontinuation of DAYPRO [oxaprozin] therapy. Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish DAYPRO [oxaprozin] from benzodiazepines."
Fortunately, if you get a test result that you believe is inaccurate, there are a variety of different confirmatory tests that can be completed, which include gas or liquid chromatography with mass spectrometry. These tests actually identify specific compounds in a given sample and don't rely on antibody reactions.
If you aren't able to have a confirmatory test, it may be helpful to see whether or not you can take the test again and discontinue or "hold" all non-essential medications for a few days to decrease the likelihood of a false-positive.
