psu123,

I strongly suggest that you not take the "test" and that you instead get a lawyer and not speak with police or prosecutors without legal counsel present. The on-line Martindale lawyer locator service may be helpful in finding a defense lawyer in your vicinity:

http://www.martindale.com

That the prosecutor would offer to drop charges if you "pass" a pseudocientific polygraph "test" is a good indication that the case against you is weak. Sometimes, such offers to drop charges are made contingent upon the suspect signing an agreement stipulating in advance that the results of the "test" will be admissible as evidence in court. If the suspect "fails," this may enable the prosecutor to win an otherwise shaky case. Conversely, if the suspect "passes," the prosecutor loses nothing (and perhaps gains political cover for the decision to drop charges).

It would be foolhardy for you to sign any such stipulation agreement, or to submit to a polygraph interrogation. Polygraphy is sheer pseudoscience, and telling the truth is no guarantee that you will pass. As used by police, polygraph "testing" is often little more than a pretext for luring a suspect into a hostile interrogation in the absence of legal counsel.

If you haven't already done so, download The Lie Behind the Lie Detector and see especially chapters 1 and 3.

With regard to the effects of anti-anxiety (or any other) medication on polygraphy, there is virtually no meaningful research on this subject.