Creating powdered urine to PRESERVE certain drugs (but exclude others)?

[kailey_elise]

I know that one method of passing a urine screen is to use reconstituted powdered urine. Via a forum search, I even got my question as to whether or not one could create their own powdered urine answered (look to Section 9.2 to jump to the part about powdering urine).

However, one question remains: if one has a detectable drug in their system, will it remain detectable upon reconstitution?

For instance, say someone takes medication that they get tested on, but occassionally likes to ingest substances they aren't prescribed. Oh, like someone who's prescribed Ritalin and they planned on taking Vicodin in the future, but their doctor tests to make sure they're taking the Ritalin as prescribed. Or someone's on Lithium and wants to smoke pot but they get their Lithium levels checked via urine. So they want to save some urine from before they used a substance that's checked for that they AREN'T prescribed, but want the substances they ARE prescribed to show up.

If that person saved their urine and dehydrated it, would the detectable levels in the urine remain, well, detectable? Or could they be messed up/destroyed during the dehydration process?

Thanks in advance!

~K.Elise