FYI Midol Works Too! Richie's Vicodin Defense...

Nicole Richie is telling friends that the reason she was on the painkiller Vicodin during her recent arrest was to treat menstruation cramps. Richie, 25, was arrested early Monday morning for driving under the influence of marijuana and Vicodin, after she was seen driving the wrong way down a California highway.

Vicodin is an opiate and Richie's involvement with the drug raises concern because she was once hooked on heroin, and former addicts who dabble in other drugs risk relapse. But pals of the Simple Life star insist that Richie has changed her ways since completing drug rehab in 2003.

"She knows she made a mistake, but overall she's in a better place," says a close friend of Richie. "She has come a long way from her heroin days." The celebutante is said to be upset over media reports that she's addicted to pills, and is insisting to friends that she only "occasionally" takes Vicodin once a month at the start of her menstruation cycle.

Richie is also unhappy that California cops listed her weight at 85 pounds on the police report because "she's so proud of her weight gain," says the source, who adds that Richie has gained about ten pounds in the last two months and actually weighs around 95 pounds. "She doesn't know where the cops came up with 85 pounds and it's annoying to her."

The embattled reality star spent Tuesday afternoon on the L.A. set of a music video for Good Charlotte with Joel Madden, 27, the band’s front man and Richie’s current flame. She is now resting at her West Hollywood condo.

Richie's rep has no comment.

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