Betsy,

I'm no expert but from what I have gleamed is that drugs have signatures or definitions much like computer viruses. If the tests look for the methylphenidate signature, they'll return a positive. I don't know, so proceed with caution - I don't thinks most pre-employment tests target the methylphenidate (Ritalin) signature. Adderall, on the other hand, because it contains the notorious dextroamphetamine will pop-up red flags out the kazoo.

Bob