LONDON: Kelly Osbourne became addicted to Vicodin by the time she was 17.

The reality TV star - who has been in rehab four times - first experienced the effects of the strong opiate when she had her tonsils taken out at 13 and admits she enjoyed the feeling it gave her.

Around three years later she was offered it in pill form and was soon taking up to 50 tablets a day because it gave her the confidence to cope with the new-found fame she had due to appearing in MTV show 'The Osbournes' and helped her cope with her mother Sharon's cancer battle.

In her new book 'Fierce by Kelly Osbourne', she reveals: "By this point I was waking up and emptying six Vicodin into my hand. Soon I was taking 50 pills a day. Most people would overdose on 10. My friends called me 'Noddy' because I fell asleep all the time.

"My parents suspected. Mum would say, 'Darling, are you taking something? Please tell your mummy.' But I was good at lying."

However, Kelly's parents, Sharon and legendary heavy metal hellraiser Ozzy, soon discovered their daughter was lying and sent her to Malibu's Promises clinic to get help.

Although she spent 30 days there receiving treatment, Kelly admits she wasn't ready to beat her addiction and did a further three stints in different rehab centres with the last one finally making her realise she had a serious problem.

Kelly, 24, said: "After 30 days, I left rehab. For the first time, I felt hopeful. I knew I'd been given another chance at my life, at my career, at happiness. I wanted to grab it."