If you are trying to find an over-the-counter medication that will produce the same results as Xanax on a drug screen you are likely not to be successful. Xanax is a benzodiazpine and all drugs in this class are available only with a prescription. Additionally, there are different types of drug screens, some more in depth than others. The more indepth tests will distinguish between false positives and can better discriminate between drug classes.
If this is your concern, my advice would be for you to purchase a commercially available drug kit from your local pharmacy and, in the privacy of your own home, you can determine whether a positive result would likely result from a test.
Xanax would likely be out of your system 138 hours (almost 6 days) after the last dose. Again, an over-the-counter drug test may be of utility to determine whether a positive result is likely.
The indepth tests utilize GC MS.
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