Amy Winehouse had "replaced drugs with alcohol" prior to her death.
The Rehab singer - who was found dead in her home in Camden, north London, on July 23 at the age of 27 - "lost track of days" after drinking herself into oblivion at her flat because she was "bored" and unable to venture outside for fear the paparazzi would stalk her.
Kristian Marr, a close friend of the late singer, said: "The problem was that she replaced drugs with alcohol. White wine was her main drink and sometimes she would wake up and drink. It meant she lost track of days - for Amy there was no day or night, no Monday or Friday.
"Three months ago I popped round to her house one afternoon, found her asleep on the kitchen floor and had to help her to bed. I was worried about Amy's drinking but at the same time relieved that drugs were no longer part of the equation.'
"She'd be at home on her own bored and having a drink because she couldn't go out anywhere without the world staring at her."
While the cause of her death is not yet known, Kristian - a musician who had known the star for seven years - explained Amy thought drugs were a "dead end" and "old school".
He added to the Mail On Sunday newspaper: "The crazy thing is that recently I hadn't been nearly as worried about her as I once had been. I knew what she sounded and looked like when she was in a bad way and I had honestly seen no sign of that for the past couple of years.
"Amy thought that drugs were a dead end and she spoke of them with disdain - they were 'old school ... in the past'."
- BANG! Showbiz