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Ask Dr. D. Love Your Own Question
Dr. D. Love
Dr. D. Love, Doctor
Category: Drug Testing
Satisfied Customers: 17357
Experience:  Family Physician for 10 years; Hospital Medical Director for 10 years.
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I have been offered to go full time on a job and have to do

Customer Question

Good morning, I have been offered to go full time on a job and have to do a pre-employment drug screening. No problem I thought as I don't use street drugs. I do have asthma and am getting over a cold with a cough I couldn't shake which is from post nasal drip. As I was taking my zyrtec, sudafed, and inhaler this morning my husband joked I would now show up on meth...
JA: How long have you been dealing with the cough? Are you having any other symptoms?
Customer: I know that may seem silly, he was joking, but now I'm really worried about it.
JA: Anything else in your medical history you think the doctor should know?
Customer: No. I was just looking up to see if I had a reason to be worried. I see similar questions here that the specimen is confirmed with GC/MS, but I don't know what that is.
JA: OK. Got it. I'm sending you to a secure page on JustAnswer so you can place the $5 fully-refundable deposit now. While you're filling out that form, I'll tell the Doctor about your situation and then connect you two.
Customer: Thank you.
Submitted: 4 months ago.
Category: Drug Testing
Expert:  Dr. D. Love replied 4 months ago.

Hello from JustAnswer. This is Dr. Love and I will be glad to assist you today.

The short answer is that your husband is partly correct, but you will be fine once the GC/MS test is done.

When doing drug testing, the first step is a screening test, which is an immunoassay test. The advantage of the immunoassay test is that it is faster and cheaper. The disadvantage of an immunoassay test is that there is a fair amout of false results. Therefore, any positive test would need to be confirmed by a more accurate test, such as the GC/MS test.

While many false positive tests are never able to be explained, there are certain drugs that are known to cause false positive. And one of the known drugs is the Sudafed, as is all of the other decongestants. All of the decongestants are chemically similar to adrenaline, but are derivatives that are made to focus on the effect on congestion. Amphetamines are also similar to adrenaline, but are derivatives that were made to focus on the stimulating effects. Since they are chemically similar, the decongestants can cross reactive with the immunoassay for amphetamines or methamphetamines, causing a false positive. However, when the sample is sent for the GC/MS test or other confirmatory test, the lab will be able to say that there is no amphetamines or methamphetamines in the sample, so you will be fine.

Therefore, it is possible that you could have a false positive screening drug test, but if so, the confirmatory test will be able to show that you have no drug in your system, and will identify the initial positive test as a false positive.

If I can provide any additional information, please let me know.

Expert:  Dr. D. Love replied 4 months ago.

Please let me know if I can provide any further assistance.

If you would like my assistance with any future questions, the question cn be directed to me through my profile at

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