Los Angeles (CNN) -- Actor Jeff Conaway is "virtually comatose" eight days after he was found unconscious from an overdose of painkillers, his manager said Thursday.
"His last movement was Sunday," Phil Brock said. "He turned his head slightly, but they have no other functions now."
Conaway, 60, who was in the TV series "Taxi" and the movie "Grease" more than three decades ago, was rushed to an Encino, California, hospital on May 11. He apparently had been unconscious for eight or nine hours before he was found, Brock said.
"It is very serious," he said. "I cannot underestimate the seriousness of this."
"Aside from drugs, he's a really wonderful soul, a very kind and wonderful person," Brock said.
Conaway's struggle with alcohol and drug addiction was chronicled in 2008 on the TV reality show "Celebrity Rehab With Dr. Drew."
Dr. Drew Pinksy, who treated Conaway on the show, released a statement Thursday.
"I am deeply saddened to learn of Jeff's condition," he said. "My thoughts and prayers are with Jeff and his family."
Pinsky also planned to comment further about Conaway on his HLN show, "Dr. Drew," which airs at 9 p.m. ET Thursday.