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What causes positive marijuana in drug test after taking Promethazine cough syrup?

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General & Family Physician
Practicing since : 2001
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I have recently took a drug screening (urine sample), the results where positive for marijuana. But the only medication I was taking was Promethazine cough syrup that was prescribed by my doctor. I would like to know how is this possible. Is there any way that Promethazine can trigger this result,because I am not a smoker.
Posted Thu, 30 Jan 2014 in Medicines and Side Effects
Answered by Dr. Michelle Gibson James 51 minutes later
Brief Answer: it can cause a false positive Detailed Answer: HI, thanks for using healthcare magic Promethazine can cause false positive results in drug testing . It can cause possibly false positive results for marijuana and in some cases amphetamines. Other drugs that can cause false positives are protonix, hemp and some NSAIDS (ibuprofen, naproxen). You may want your doctor to speak to the persons conducting the test. Normally a second test is done to check the result of this initial screening tests. The second test is usually a more specific and accurate test that would be able to clarify the situation. I hope this helps,feel free to ask any other questions
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Follow-up: What causes positive marijuana in drug test after taking Promethazine cough syrup? 7 minutes later
Would it be possible for you to provide me with some more in depth details about this. It will be helpful to me.
Answered by Dr. Michelle Gibson James 4 hours later
Brief Answer: hope this helps Detailed Answer: HI False positive drug results can occur in 5 % up to 10 % of persons who have these tests done. The accuracy of a test depends on the assay (lab detecting method) and the substance being investigated. These false reaction may occur because the breakdown products of the medication interact with the test. Potentially false positive results are subsequently followed up using a more accurate testing method ( the GC-MS lab method).
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