What Medications Will Test Positive for Benzodiazepines?

Several medications that are not benzodiazepines can trigger a positive result on a standard urine drug screen for this drug class. The most well-documented culprits include the antidepressant sertraline, the HIV medication efavirenz, the anti-inflammatory drug oxaprozin, and the antipsychotic quetiapine. At the same time, some prescribed benzodiazepines are routinely missed by the same tests, creating a confusing picture where the screen catches drugs it shouldn’t and misses drugs it should. Understanding both sides of this problem matters whether you’re a patient, a prescriber, or someone facing a workplace or legal drug test.

How the Screening Test Works and Why It Makes Mistakes

Standard urine drug screens for benzodiazepines use a technology called immunoassay. The test relies on antibodies designed to recognize and bind to benzodiazepine molecules or their breakdown products. When a urine sample contains enough of a substance that looks like a benzodiazepine to those antibodies, the test reads positive. The key word is “looks like.” These antibodies are not perfectly selective. Any molecule with a chemical shape similar enough to a benzodiazepine can fool the antibody into reacting, producing a false positive. This cross-reactivity is the root cause of nearly every medication-related false alarm on a benzodiazepine screen.

Because screening tests are designed to cast a wide net, they are considered presumptive. A positive result on an immunoassay is not proof that a benzodiazepine is present. Confirmatory testing using more precise laboratory methods is needed to identify exactly which substance triggered the result. Despite ongoing improvements in antibody design, immunoassay drug screens remain presumptive and still require confirmation by more specific techniques.

Medications That Cause False-Positive Benzodiazepine Results

The list of medications reported to trigger false positives for benzodiazepines is shorter than you might expect, but each entry is well documented.

Sertraline (Zoloft)

Sertraline, one of the most commonly prescribed antidepressants, has been linked to false-positive benzodiazepine screens. A retrospective chart analysis reviewing over 500 records found that of 160 confirmed false positives, 26 were associated with sertraline use after other explanations were ruled out. The researchers concluded that sertraline may be an unreported cause of false-positive benzodiazepine results in a widely used screening assay.¹ This is worth knowing because sertraline is prescribed to millions of people for depression and anxiety, and a false positive could lead to unnecessary suspicion or clinical confusion.

Efavirenz (Sustiva)

Efavirenz, an antiretroviral drug used to treat HIV, is arguably the most dramatic offender. In a study of 100 HIV-positive patients, 49 out of 50 patients taking efavirenz tested positive for benzodiazepines on at least one drug screen, compared with just 1 out of 50 patients not taking the drug. The cross-reactivity was traced to a specific metabolite called 8-hydroxy-efavirenz, which apparently mimics a benzodiazepine closely enough to fool the antibody.² If you take efavirenz and are facing any form of drug testing, this is something both you and your testing provider need to be aware of.

Oxaprozin (Daypro)

Oxaprozin is a prescription nonsteroidal anti-inflammatory drug (NSAID) used for arthritis. Research has shown that oxaprozin and its metabolites cross-react with at least three commercial benzodiazepine immunoassays, producing presumptive positive results.³ This is specific to oxaprozin. A separate prospective study collecting over 500 urine samples from people taking common over-the-counter NSAIDs like ibuprofen, naproxen, and fenoprofen found no false positives for benzodiazepines.⁴ So if you take ibuprofen for a headache before a drug test, you do not need to worry about a benzodiazepine false positive.

Quetiapine (Seroquel)

Quetiapine, an atypical antipsychotic used for conditions like schizophrenia and bipolar disorder, has been reported to trigger false-positive benzodiazepine screens. In one documented case, a patient started on quetiapine and lorazepam had a urine drug test on his third hospital day that came back positive for benzodiazepines, with the result attributed in part to quetiapine’s cross-reactivity with the screening assay.⁵ Case reports like this are less robust than controlled studies, but quetiapine appears in reviews of false-positive drug screens frequently enough to warrant awareness.

Benzodiazepines That Commonly Get Missed

Here is the less intuitive side of the problem: if you are actually taking a prescribed benzodiazepine, there is a real chance the screening test will miss it. False-negative rates for benzodiazepine immunoassays can be surprisingly high. One analysis reported a false-negative rate of roughly 47% when immunoassay was used to screen for benzodiazepines.⁶ That means nearly half the time someone was actually using a benzodiazepine, the test said they weren’t.

The reason comes down to how your body processes different benzodiazepines. Most screening assays were originally calibrated to detect older benzodiazepines like diazepam and its metabolites, particularly nordiazepam and oxazepam. Drugs like lorazepam, clonazepam, midazolam, and flunitrazepam are metabolized differently. Lorazepam, for example, is primarily converted into a glucuronide metabolite in the body, and that glucuronide form is what ends up in urine. The problem is that many immunoassays have poor cross-reactivity with glucuronide metabolites. A spiking experiment confirmed this directly: one commonly used assay (the Abbott MULTIGENT) detected lorazepam itself at all concentrations tested but completely failed to detect lorazepam glucuronide, which is the form you’d actually find in a patient’s urine.⁶

Midazolam, chlordiazepoxide, and flunitrazepam have similarly poor detection across many commercial assays. Detection is manufacturer-specific and antibody-specific, which means the same patient’s urine could test positive on one brand of test and negative on another.⁷ This has real clinical consequences: a doctor monitoring a patient’s compliance with a prescribed benzodiazepine may incorrectly conclude they are not taking their medication based on a negative screen, when the test simply cannot detect that particular drug.

The Hydrolysis Fix

Laboratories have found a workaround for the glucuronide detection problem. Adding an enzyme called beta-glucuronidase to the urine sample before running the immunoassay breaks the glucuronide bond, converting those hard-to-detect metabolites back into forms the antibodies can recognize. Assays that incorporate this hydrolysis step show substantially better clinical sensitivity than those that do not.⁸ One high-sensitivity version of a Roche assay adds beta-glucuronidase to improve detection of these common urine metabolites.⁹

The difference is not subtle. Immunoassays using enzymatic hydrolysis (like the KIMS II and CEDIA platforms) consistently outperform those that skip this step (like the EMIT II Plus) in detecting both prescribed and non-prescribed benzodiazepines.¹⁰ Not all labs use hydrolysis-enhanced assays, though, which means the accuracy of your test depends partly on which laboratory processes your sample. You generally have no way to know which assay platform a lab uses unless you ask.

Why Results Vary Between Testing Platforms

The variation between different commercial immunoassay kits is a genuine problem for anyone interpreting test results. A comparison of five commercial benzodiazepine immunoassay kits found that results were not consistent among the kits evaluated, even when testing the same substances at the same concentrations.¹¹ One kit might flag a sample as positive while another, testing the same urine, calls it negative. This variation exists because each manufacturer uses a different antibody targeting a slightly different part of the benzodiazepine molecule, and each manufacturer sets its own cross-reactivity profile.

This matters most in clinical settings where a patient’s care plan depends on the test result. If a pain management clinic uses one assay platform and a substance abuse program uses another, the same patient could get contradictory results. Understanding that benzodiazepine screening is not a single standardized test but a family of different assays with different strengths and blind spots goes a long way toward making sense of confusing results.

Non-Benzodiazepine Sleep Medications

A common concern is whether “Z-drugs” like zolpidem (Ambien) will show up as benzodiazepines on a drug screen. These medications target similar receptors in the brain but have a different chemical structure. An early study found that zolpidem did not cross-react with standard urine drug screens for benzodiazepines, opiates, barbiturates, cocaine, cannabinoids, or amphetamines at any time point after ingestion.¹²

However, a later study using a different type of immunoassay (ELISA kits) found that nearly all urine samples from zolpidem users screened positive, even when confirmatory testing detected no zolpidem in some of those samples.¹³ The takeaway: whether zolpidem triggers a positive depends entirely on the specific assay kit being used. Standard workplace immunoassays generally will not catch it, but certain ELISA-based kits might.

Designer Benzodiazepines

A newer wrinkle in benzodiazepine testing involves non-FDA-approved benzodiazepines, sometimes called “designer benzodiazepines,” that are sold online or appear in counterfeit pills. These substances are chemically related to prescription benzodiazepines and are often potent, but they are not included in standard confirmatory test panels. A study examining 35 emergency department urine specimens that initially appeared to be false-positive benzodiazepine screens found that standard confirmatory testing using a 19-component panel detected no prescribed benzodiazepines. Expanded testing, however, revealed the presence of designer benzodiazepines that the screening immunoassays had correctly detected but the confirmatory method could not identify.¹⁴

This creates a paradox: the less specific screening test was actually picking up a real substance, but the more specific confirmatory test missed it because it was not programmed to look for that particular molecule. Laboratories using traditionally designed confirmatory panels may fail to identify these substances, leading clinicians to dismiss the screening result as a false positive when it was actually a true positive for a substance not on their radar. Screening assays from all three major manufacturers tested showed cross-reactivity with multiple non-FDA-approved benzodiazepines, suggesting the screens are doing their job but confirmatory methods have not caught up.¹⁵

Herbal Products and Supplements

An occasionally overlooked source of positive benzodiazepine screens is adulterated herbal supplements. In one documented case, a female athlete tested positive for benzodiazepines on a random drug screen despite denying all prescription and illicit drug use. Investigation revealed that a Chinese herbal product she was taking, marketed as “Miracle Herb,” contained undeclared diazepam as an additive.¹⁶ This was not a false positive in the chemical sense; the test correctly detected a benzodiazepine that the user did not know she was taking. Supplements marketed for relaxation, sleep, or pain relief and sold outside standard pharmaceutical regulation are the most likely to contain unlisted pharmaceutical ingredients.

What to Do If You Get an Unexpected Result

If a drug screen comes back positive for benzodiazepines and you are not taking one, the single most important step is to request confirmatory testing. Confirmatory methods like liquid chromatography with tandem mass spectrometry can identify the exact molecules present in the sample, distinguishing a true benzodiazepine from a cross-reacting medication. This confirmation is not optional in any high-stakes situation like employment screening, legal proceedings, or medical decision-making.

It also helps to provide a complete medication list at the time of testing. Knowing that a patient takes sertraline or efavirenz lets the testing provider and the clinician interpret the result in context before jumping to conclusions. Some testing facilities will note known cross-reactive medications on the requisition form so that results can be flagged for follow-up rather than acted on immediately.

The same logic applies in reverse. If you are prescribed a benzodiazepine and your screen comes back negative, that does not necessarily mean you are not taking it. As covered earlier, certain benzodiazepines are simply invisible to certain assays. Laboratories using hydrolysis-enhanced immunoassays will catch more true positives, but not every facility has upgraded to those platforms.

Oral Fluid Versus Urine Testing

Some testing programs use oral fluid (saliva) instead of urine for drug screening. A comparison of the two found that urine is the better matrix for detecting benzodiazepines. In one study, all urine samples that screened positive by immunoassay were confirmed to contain benzodiazepines by mass spectrometry. But among the corresponding oral fluid samples from the same individuals, only four tested positive. Concentrations in oral fluid were, with one exception, lower than in urine, making detection harder.¹⁷ If you are being tested by saliva swab and take a benzodiazepine, there is a meaningful chance the test will not pick it up, especially at low or moderate doses.

This difference is relevant for compliance monitoring in pain clinics or substance abuse programs. A provider relying solely on oral fluid screening may underestimate actual benzodiazepine use. Conversely, oral fluid testing has a narrower detection window, which can be an advantage when the question is about very recent use rather than use over the past several days.

A Quick-Reference List

For easy scanning, here are the categories of medications and substances that interact with benzodiazepine drug screens:

• Known false-positive triggers: sertraline (Zoloft), efavirenz (Sustiva), oxaprozin (Daypro), quetiapine (Seroquel)
• Not a concern for false positives: ibuprofen, naproxen, fenoprofen, and other common over-the-counter NSAIDs
• Frequently missed by standard assays: lorazepam, clonazepam, midazolam, flunitrazepam, chlordiazepoxide
• Variable depending on assay: zolpidem (Ambien), which generally does not trigger standard workplace tests but may trigger ELISA-based kits
• Hidden sources: adulterated herbal supplements, particularly imported products marketed for relaxation or pain
• True positives misread as false: designer benzodiazepines that standard confirmatory panels do not include

Drug screening for benzodiazepines is far from the binary yes-or-no that most people assume it is. The result depends on which medication you take, which assay platform the lab uses, whether hydrolysis is part of the process, and whether the confirmatory panel is broad enough to catch newer substances. Knowing this gives you the context to push for the right follow-up when a result does not match reality.