Can Benadryl Cause A Positive Drug Test Result For Tramadol?
In our latest question and answer, the pharmacist discusses the false-positive drug test results that can be caused by Benadryl (diphenhydramine).
Is it possible for diphenhydramine to test positive as tramadol on a urine drug screen?
Nov 01, 2022- Benadryl has been shown in studies to cause false-positive results on urine drug screens for opioids and other drugs, though no specific studies have documented this occurring with tramadol. Always tell your doctor and the testing facility about all medications you are taking before a drug test so they can account for potential false-positives. If you get a positive result you believe is incorrect, you can request a more accurate confirmatory test like gas chromatography mass spectrometry that won't have false-positive problems.
Answer
The most common type of urine drug screening utilized by employers and health care professionals is an immunoassay-based test, which uses antibodies to react to a specific drug compound (or metabolite). While these types of tests provide fast, and generally, accurate results, they are known to miss on occasion.
Specifically, the most common type of error with these tests are 'false-positives', which is when a drug compound that is not being tested for reacts with an antibody, producing a reaction, and thus gets recorded as a 'positive' result.
As it concerns Benadryl (diphenhydramine), it has been found in some studies to cause false-positive results on urine drug screenings for several different drugs, including:
- Opiates
- PCP
- Tricyclic antidepressants (e.g., amitriptyline)
Just how commonly false-positives occur when someone has taken Benadryl prior to a drug test isn't known, but it is always a good idea to disclose all of the medication you are taking prior to being tested so your doctor and tester are aware.
Benadryl Can Cause Problems With Some Drugs Tests
As mentioned, studies have singled out Benadryl (diphenhydramine) as being responsible for causing false-positives for several different drugs.
You asked about tramadol specifically, which is an opioid drug. I could not find any studies that have specifically noted Benadryl causing a false-positive for tramadol, but there is certainly plenty of evidence of it causing false-positives for other opioids.
For example, one study found that it can cause false-positives for the opioid drug, methadone:
Rapid urine drug screens using immunoassays based on the principle of competitive binding may show false-positive methadone results for patients who have ingested DPH [diphenhydramine].
Similarly, it has also been found to cause false-positives for other drugs, such as PCP (phencyclidine), a dissociative anesthetic:
False-positive urine screens for PCP are associated with tramadol and dextromethorphan and may also occur with diphenhydramine.
I do want to point out that tramadol isn't a drug that is screened for on most common drug screenings (such as the SAMHSA drug panel). The most common urine screens are 5-panel tests that look for:
- Amphetamines
- Cocaine
- Marijuana
- Opiates
- Phencyclidine (PCP)
'Opiates' refers to natural opiates, like morphine and codeine. Synthetic opioids, like hydrocodone, tramadol and oxycodone can certainly be tested for and may be included on whatever test you are taking, but I just want to point out that your standard drug test may not even be looking for those.
What To Do If You Believe You Got A False-Positive Result
As mentioned, you always want to let your doctor and your tester know about all the drugs you are taking.
At the very least, the testing agency will have a list of common drugs that cause false-positives, and if they know ahead of time, getting a false-positive result may be more easily explained and give you an opportunity to take another test.
Additionally, there are more accurate, confirmatory drug tests available (such as gas chromatography mass spectrometry) that actually look for specific drug compounds, and don't rely on antibody reactions. These can be more expensive, but don't have problems with false-positives.
Final Words
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References & sources
- How often do false-positive phencyclidine urine screens occur with use of common medications? — PubMed
- False-Positive Interferences of Common Urine Drug Screen Immunoassays: A Review — Oxford Academic
- Rapid urine drug screens: diphenhydramine and methadone cross-reactivity — PubMed
- Urine Drug Screening: Practical Guide for Clinicians — Mayo Clinic
- False positive opiate immunoassay caused by diphenhydramine — PubMed
Glossary — Terms in This Answer
- Immunoassay
- A test that uses antibodies to detect the presence of specific drugs or their byproducts in urine.
- Metabolite
- A substance produced when the body breaks down and processes a drug.
- False-positive
- A test result that incorrectly shows the presence of a drug that the person did not actually take.
- Diphenhydramine
- The active ingredient in Benadryl, an over-the-counter antihistamine medication.
- Tricyclic antidepressants
- A class of older antidepressant medications used to treat depression and other conditions.
- Opioid
- A class of drugs that includes both natural and synthetic pain-relieving medications derived from or similar to opium.
- Phencyclidine
- A dangerous dissociative drug also known as PCP that produces hallucinations and detachment from reality.
- Gas chromatography mass spectrometry
- A highly accurate confirmatory drug test that identifies specific drug compounds rather than relying on antibody reactions.
Dr. Brian Staiger, PharmD
Doctor of Pharmacy, board certified clinical pharmacist (BCPS), American Herbalist Guild, Medication Therapy Management certified
Brian Staiger, PharmD, BCPS, is a licensed pharmacist with more than 13 years of experience across retail pharmacy, clinical pharmacy, medication safety, pharmacy program development, and healthcare administration. He is the founder of HelloPharmacist.com, where he helps patients...
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