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Family Physician
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Experience:  Emergency Medicine and Family Practice for over 26 years
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could benadryl give a false positive for benzodiazapen in urine

Customer Question

could benadryl give a false positive for benzodiazapen in urine test?
Submitted: 6 years ago.
Category: Medical
Expert:  Dr. R. Bora replied 6 years ago.
Hello, welcome to just answer and thank you for your question.

Generally, most prescription sleeping pills and anti-anxiety medication cause a false postive test for benzodiazepines.

Benadryl does not cause a false positive result for benzodiazepines.


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Edited by Dr. R. Bora on 10/1/2010 at 7:28 PM EST
Expert:  Dr. R. Bora replied 6 years ago.
Benadryl (diphenhydramine ) is considered as a "non cross reactive compound" meaning that it does not cause false positve results during drug screening tests.

Here is a list of drugs which can sometimes cause false positive results during drug screening tests. Check this link to get the list.


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Expert:  Family Physician replied 6 years ago.
I believe that it is important to clarify the answer provided by the other expert.

Drug tests performed for most employment or legal purposes are performed with a 2 step method. The first (screening) test uses an immunoassay test. These tests are very sensitive, however they are not specific (i.e., they are subject to false positives).

The second (confirmation) test is done with GC/MS (or the similar LC/MS). The GC/MS confirmation test are very specific (think of this like a "chemical fingerprint"). There are no causes for false positives if the test has been confirmed with GC/MS.

The only reported causes of false positive screening tests for benzodiazepines are oxaprozin (Daypro) and sertraline (Zoloft). If the test was not confirmed with GC/MS and you have not used any benzodiazepine (diazepam, alprazolam, lorazepam etc), the GC/MS confirmation test would be negative.

You need to check with if the test was confirmed with GC/MS.

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