The 73-year-old actor and artist is being treated through a "special program" at the University of Southern California, said Sam Maydew.
Asked about Hopper's prognosis, Maydew said, "We're hoping for the best." He would not elaborate on the actor's condition.
Hopper was forced to cancel his appearance at an exhibition of his artwork and photography at the Australian Centre for the Moving Image in Melbourne. Called "Dennis Hopper and the New Hollywood," the show celebrates "the work and life of an extraordinary filmmaker, artist and key figure in the evolution of Americas cultural scene from the 1950s to today."
Hopper was hospitalized in New York earlier this month and treated for dehydration.
The "Easy Rider" star recently finished shooting the second season of "Crash," a TV version of the Oscar-winning 2004 film. He plays maniacal music producer Ben Cendars on the series, which airs on the Starz network. Hopper also has several film projects in the works.