Denise Richards is never surprised by Charlie Sheen's behaviour because partying is just part of his lifestyle.

The 'Two and a Half Men' star's ex-wife - who he has daughters Sam, six, and five-year-old Lola with - admitted the actor's recent troubles, including a stay in hospital after a 36-hour drink and drug binge with porn stars, have not shocked her.

She said: "It doesn't surprise me. I mean, you know this is Charlie's lifestyle. He makes no bones about it. And it is what it is."

Denise - who divorced the 45-year-old actor in 2006 after four years of marriage - also revealed she struggles with how to explain the situation to the couple's children and is unsure of how much they understand about their father's addictions.

Speaking on US TV show 'The View', the 39-year-old star said: "What can you say? It's a very difficult situation in dealing with the subject. This has been something I have dealt with for years. This is not a new situation. There are times where his life is more colourful than others, more public than others, and as the kids get older it's a difficult thing.

"I'm learning as I go too. I have never had to deal with this and this was a subject I had hoped to talk with my children about as they got older. But it's hard. I mean there are books that are out there. One in particular, I'm blanking on the title, it explains addiction to children. There are images and pictures that a child can understand. I don't know what they fully comprehend from these conversations. They don't know what some of these things are. So I do the best I can and it's not easy."