Heather_locklear240 Heather Locklear has been formally charged with a DUI, according to the Santa Barbara, Calif., District Attorney’s Office.

But it wasn’t alcohol. And there were no illegal drugs in her system.

It was prescription drugs. Remember Locklear did four weeks of treatment in July for anxiety and depression.

"Lab tests showed she had no alcohol in her system and no illegal narcotics of any kind," says Senior Deputy District Attorney Lee Carter, who declined to comment about the medications – or the amounts – she took. He added "We believe that the prescriptions she was taking could have impaired her ability to drive a motor vehicle safely."

The former Melrose Place star was arrested Sept. 27 in Montecito after a paparazzo dialed 911 to report that Locklear was "driving erratically."

Which is pretty nice of the papper. Most of them would have just followed her and photographed whatever crash she got into for big bucks.

Heather will be arraigned on Jan 26, 2009 in Santa Barbara court.

Happy New Year….

Photos: Santa Barbara County Sheriff’s Department

More on Heather Locklear:

Heather’s depression: Is it "Complicated?"

Posted by:Elizabeth Snead