Eminem "wiped out five years" of his life with prescription drugs.
The "Love the Way You Lie" rapper fought a battle with drug addiction which came to a head after his 2004 album Encore which resulted in him taking five years off before making a comeback.
The hip-hop star admits his substance abuse problems were so bad he has lost whole years of his memory.
He told Rolling Stone magazine: "I try to stay recording, because if I don't, I get rusty. I'm very paranoid about writer's block—I had it for four years, and it drove me f***ing crazy. No matter how hard I tried, I just couldn't think of s**t.
"The pills had a lot to do with it. Just wiping out brain cells.
"I don't know if it sounds like I'm making excuses, but the absolute truth is a lot of my memory is gone.
"I don't know if you've ever taken Ambien, but it's kind of a memory-eraser. That s**t wiped out five years of my life.
"People will tell me stories, and it's like, 'I did that?'
"I saw myself doing this thing on [TV network] BET recently, and I was like, 'When was that?'"
The 38-year-old rapper still wrote music during the heaviest period of his addiction, but admits that looking back over his words from that period is a difficult experience.
He added: "It f***ing creeps me out. Letters all down the page—it was like my hand weighed 400 pounds. I have all that s**t in a box in my closet. As a reminder that I don't ever want to go back."
Eminem's drug problems began in 2002 when he made the semi-autobiographical movie 8 Mile and got worse on subsequent tours.
He said: "We were doing 16 hours on the set on 8 Mile, and you had a certain window where you had to sleep.
"One day somebody gave me an Ambien, and it knocked me the f**k out. I was like, 'I need this all the time.'
"Then, when I got off probation for my felonies [in 2003], and I didn't have to drop urine anymore, the reins came off. On the Anger Management 3 tour [in 2005], I was f***ed up every night."
Eminem eventually overcame his demons and has been clean and sober since 2007.