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 behaviour, 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 apologised, 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 programme 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: "Recognising 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 programme 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.