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How does Charlie Sheen do it?

After a series of wild nights with porn stars and booze, hospital stays, and well-publicized arrests, his employer still has his back.

A top exec at CBS said Friday that the network is concerned about Sheen's off-camera behavior, but it hasn't affected his work as the star of television's most popular comedy.

"We have a high level of concern," said Nina Tassler, CBS entertainment president. "How can we not?"

The actor's recent headlines have included a wild night that left a New York hotel room in shambles and sent Sheen to a hospital, and a guilty plea last summer to assaulting his wife in Aspen, Colorado.

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Sheen filled gossip pages again by spending last weekend partying in Las Vegas.

Tassler said she has given a great deal of thought to Sheen on a "human level," but the situation can't be viewed simplistically. The actor does his job reliably well on "Two and a Half Men," she said.

A reporter suggested a person in a different line of work would be fired for involvement in similar incidents.

"What do you get fired for? Going to work and doing your job?" Tassler asked.

Sheen's Monday night program has increased its audience by 2 percent over last season, the Nielsen Co. said. He signed a new two-year contract at the end of last season that makes him one of the highest-paid actors on prime-time television.

CBS respects the way Warner Bros. Television, the producer of "Two and a Half Men" and Sheen's actual employer, has been handling the situation, Tassler said.

"This show is a hit," she said. "That's all we have to say."

- The Associated Press contributed to this report.