London, Jan 5 (ANI): Britney Spears' much-publicised meltdown that landed the singer in hospital can be attributed to a deadly combination of narcotics, including a drug designed to make racehorses leaner.

According to reports, in addition to the horse drug, the 'Toxic' singer is heavily dependent on "recreational" substances such as crystal meth, speed and ecstasy, all of which are taken with huge quantities of vodka. pears is currently being held for mental evaluation at Cedars-Sinai Medical Center in Los Angeles, following police and paramedical intervention in her house on Jan 3.

The singer had a face-off with police at her home after refusing to turn over her sons to ex-hubby Kevin Federline's bodyguard, following which cops and medics strapped her to a gurney and took her, by ambulance to Cedars-Sinai, where she will be held for 72 hours to for mental evaluation.

Sources close to the Toxic star said fears had been growing over her drug habits and she was clearly "on the edge".

When her career collapsed, Britney began taking clenbuterol, known as clen, believing it would help her lose weight and tone her body.

"Clen is a drug originally created for racehorses which helps them breathe. It makes them lean and muscular and has the same effect in humans. It works much better if you eat loads of junk - so it seemed perfect for Britney," The Sun quoted a source, as saying.

"The drug has played a big part in her meltdown this year. She started taking it after her marriage fell apart so she could get herself back into the same shape she was in before she had her kids. The side effects are horrific if you binge on clen. It makes you behave hysterically and act like a maniac.

"If you take it for more than six weeks it can be harmful too - and she has been doing just that," the source added.

One of the officers from the Los Angeles Police Department said that Spears was "believed to be under the influence of some kind of drug."

Another source revealed that Spears had lost a lot of weight recently because of mental anguish and her drug habits.

"She is on the edge. The custody battle with Kevin and the constant attention on her life is too much for her to bear. She was hysterical when police arrived and said she just wanted to keep the kids for the night," the source said.

Following the singer's hysterical antics, a Los Angeles judge has awarded the "sole legal custody and sole physical custody" of Sean Preston, 2, and Jayden James, 1, to Spears' Federline, until another hearing on January 14. (ANI)