Veteran hellraiser Keith Richards has been forced to quit cocaine, because he can't mix it with the drug doctors have prescribed him after he fell out of a tree last year (06). The 63-year-old Rolling Stone, a former heroin addict and longtime party animal, suffered a head injury when he slipped out of a palm tree in April 2006. And he now has to take a drug which cannot be taken with cocaine. Richards says, "Drugs I'm on now - the s**t I've gotta take because of the brain job, Dilantin. Means you can't take cocaine anymore. Which is fine with me. "I mean, I haven't seen coke for, like, a year and a half. Big deal. Y'know I used to like my little bump here and there after meals. But now I can't do that anymore, so I don't do it no more. "I still smoke like a f**king chimney. Get me some good weed."