Pharmacy/urine screen


Dr. Ghooi,
I saw from an earlier question that it is hard to calculate a urine screen test but I would like to know your professional opinion about this one. I took one 2mg alprazolam tablet and have a urine drug screen that detects up to 50ng/mL. I took the tablet at 5:00pm on saturday and have the test 4:30pm on tuesday. (My urine was completely clean from any sort of benzodiazepine before this tablet.) I am 5'1 108 pounds. can you tell me around what ng/mL it could be? (one time i took one 2mg tablet on saturday and on MONDAY i failed) will one day make a difference this time? thank you so much

Hi Laura,
You are right about the difficulty in calculating the drug level in urine. But let me try, though I dot know how accurate I will be, hnece I do hope I do not mislead you.
My first advice is, can you put off your test till weekend, any excuse will do. If not here is the prediction. Your weight is 49 kg and hence I calculate your blood volume to be 5.3 L.
Alprazolam has a half life of 11.2 hours (range: 6.3 to 26.9 hours). Due to the wide intraindividual difference, it makes calculation all the more difficult, so we will calculate for extremes. Following a 3 mg dose the maximum plasma level is 37 ng ml. In the absence of more accurate data I am forced to base all my calculations on this.

Cmax          37 ng/ml

Level after 24 hours          9.25 ng/ml
Excretion in the first 24 hours          27.75 ng x 5300 = 147 mcg

Level after 48 hours          2.31/ng/ml
Excretion in the second 24 hours          6.9 ng x 5300 = 36.7 mcg/ml

Level after 72 hours          0.57 ng/ml
Excretion in the third 24 hours          1.73 ng/ml x5300 = 9.169 mcg

Let us assume you drink adequate water, and that there is not much sweating in your area. This means you should be passing about 2.0 L of urine daily. You took a 2 mg tablet on saturday at 5.00 pm, then by sunday 5. 00 pm you would have a urinary level of 73.5 ng per ml in your urine.
Going by this formula on monday at 5.00 pm you would have a level of 18.3 ng/ml in urine
On tuesday by 5.00 pm you would pass 4.5 ng/ml in urine.
I am worried about this level, they might be able to detect it. If you cannot put off the test, I suggest you drink a lot of water on sunday, monday and tuesday. Pass urine before you go for the test and drink again a lot of water. What we are trying is to increase urine volume which would reduce the concentrtion of the drug in the urine.
I do hope you pass the test, else I shall feel very guilty about all this. But do let me know what happens.
Best wishes
Ravi Ghooi  


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Dr. Ravindra Bhaskar Ghooi


I can provide information on drugs and medicines, their actions, uses, interactions and adverse effects. To avoid confusion, generic names of medicines may please be provided. I am a pharmacologist, having worked on animal and human pharmacology, and presently I am the Dean of Bilcare Research Academy, where we teach courses on clinical research. We dont work on saturdays and sundays, hence questions reachng me on these days will be replied on Monday, please bear with me.

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