Michael Madsen was reportedly treated at a London hospital after being found unconscious on the doorstep of a hotel in the capital.
The Reservoir Dogs star was in the UK earlier this month to make a low-budget horror film when he apparently went on a nine-day booze and pills bender.
According to The Sun, Madsen, 52, was placed on suicide watch at the Royal Cornwall Hospital in Truro. An insider said staff at the Penventon Park Hotel were shocked at the amount of alcohol Madsen consumed.
"He was mixing his drinks with pills, but no one knew what they were for. He angered some guests by urinating in the car park. When he was found slumped on the doorstep it was hardly a surprise," the insider said.
Madsen, who played Mr Blonde in the 1992 Quentin Tarantino movie, was last night said to have returned to the US.