Jenna Jameson claims she can prove Tito Ortiz wasn't telling the truth when he accused her of being high on OxyContin during their altercation Monday morning -- because we've learned Jenna passed a drug test one day after the incident.


We've learned the results of the test, administered Tuesday by American Toxicology Inc. in Las Vegas, show Jenna's urine tested "negative" for the ten major drugs they were screening for ... a list that included cocaine, weed, meth and oxycodone -- the major ingredient in OxyContin.

As we previously reported, Tito was arrested Monday for felony domestic violence.  After he was released, Tito claimed the incident was triggered by Jenna's addiction to OxyContin -- a claim Jenna vehemently denied.

Now, after receiving the results of the test, Jenna is reaffirming her claim telling us, "I am definitely not addicted to OxyContin or any drug."

Jenna's powerhouse attorney Ronald Richards added, "The lab tests clearly exonerate Jenna Jameson of any hint, iota, or suggestion that she ingested or was under the influence of any opiates or controlled substances."

Richards continued, "Statements made by anyone to the contrary are completely impeached by the results from this prestigious testing facility."