Charlie Sheen was taking too much cocaine to work when filming 'Two and a Half Men'.
Production on the sitcom was stopped after 16 episodes of its eighth series earlier this year because of the actor's erratic behavior, and the series' co-creator, Chuck Lorre, said he had no choice but to take drastic action out of concern for the star.
He told TV Guide magazine: "You can't do that much cocaine and work. I didn't want to be writing a sitcom while my friend died. Or worse, hurt someone else.
"We couldn't be complacent. There was a tragedy unfolding right in front of us. There was violence and blackouts. On a certain level, if you're looking the other way, you're responsible.
"It was falling apart. It was heartbreaking to be around here then."
Charlie left the show in February, launching a number of rants against Chuck, although he has now apologized, and been replaced on the show by Ashton Kutcher.
Meanwhile, Charlie's ex-wife, Brooke Mueller - with whom he has two-year-old twin sons Bob and Max - is entering a program of outpatient rehab, which includes daily drug testing and round-the-clock private supervision, following her arrest by police for cocaine possession in Colorado earlier this month.
A statement from her publicist said: "Recognizing past attempts at treatment have not been successful, Brooke has decided to take a different approach to deal with her addiction.
"Brooke will be participating in a program during the day, and will be under expert supervision 24 hours a day, seven days a week."
Brooke will retain custody of Bob and Max, keeping them at her home along with their nanny while she undergoes treatment.