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Dr. Kaushik
Dr. Kaushik, Psychiatrist
Category: Mental Health
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Experience:  MD Psychiatry
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Why is my husbands clonazepam not showing in a urine drug

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Why is my husband's clonazepam not showing in a urine drug screen when he is taking 2mg a day?

Hi there ,


Welcome to Just answer !


1) Well, i would like you to tell me that whether your husband had stopped taking clonazepam 2 mg / day , prior to his urine test and if yes then how many days after his stopping of intake of clonazepam , was his urine test carried out ?


2) Also , kindly mention how he used to take 2 mg of clonazepam /day , that is what time of the day and in what doses ?


Kindly answer the queries against their numbers and i shall get back to you with an appropriate reply.



Customer: replied 7 years ago.
Thank you for replying.

1) No, he did not stop taking his medication prior to the UA. I do his medicine box and give him his medication, so I know it was in there.

2) He was taking .5 mg tablets 2po qam & qpm

Approximately 7am and 7pm

I know it is metabolized through the liver, excreted through the kidney and less than 2% of whole clonazepam is found in the urine. It is fast absorbing, protein-binding and has 90% absolute bioavailability, and maximum concentration is reached in 1-4 hours. The best test for clonazepam is a serum blood test.

What I don't understand is why exactly it does not show in a UA and why this test would be used to dc the med abruptly when a taper is necessary since withdrawal symptoms can range from the minor to severe, especially with pre-existing severe health problems.

My husband is a nurse and I am in pharmacy.

Thanks for the reply .


Good to know that you know the pharmacokinetics of Clonazepam , and so the reason why the drug , which has a high first pass metabolism and is excreted less than 2 percent in urine , did not show in urine test , is because it was most probably a FALSE NEGATIVE test , meaning that either due to operator related error or due to the error of the testing parameter the traces of the drug were missed form being shown in urine sample .


So,it is always recommended to relate the history of patient's intake of drug , and the outcome of the test , as in case of your husband there is discrepancy between the two , so . the doctor who was advicing you at that time should have asked for a repeat urine test from a different patholab , and let me tell you that such kind of errors are not uncommon..


Now, irrespective of the urine test results , all the psychotropic drugs including clonazepam , need not be stopped abruptly , because of the withdrawl symptoms it can produce if stopped abruptly , so a psychiatrist should always have such a possibility in mind whle decreasing the dose of clonazepam or any other psychotropic drug for that matter , and should not get influenced by the test reports , and lay more stress on his clinical skills .


I am really sorry to say that a lack of insight and common sense on part of the treating doctor lead to such anxious moments to yourself and your husband .


So, as of now , there is no point in going for a repeat of urine test , as by now , the drug must have been excreted out completely ( clonazepam has a half life of 30 - 40 hrs ) , so , if your husband is managing the withdrawl symptoms well enough then there is no need to worry , plus it will be just 1-2 weeks , that he has to endure these withdrawl symptoms , if at all there are any.


I hope this helps..


I wish your husband all the best .


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