Jeff Conaway lies in a hospital bed in Encino, Calif., in a coma with doctors fearing for his life.

The actor, best known to genre fans as Security Chief Zack Allen in "Babylon 5," was first reported to have had an intentional drug overdose. But doctors are now saying that while drugs may not have helped him, Conaway is instead fighting pneumonia and a blood infection.

What happens to him between now and Tuesday is very important, because it literally means life or death for Conaway.

The 60-year-old actor has struggled with drug addiction for many years, even having those struggles documented in the reality television show "Celebrity Rehab With Dr. Drew."

Conaway grew up in acting, and never had a chance to really enjoy a childhood. Although his first movie role came in the 1971 film "Jennifer On My Mind" (which also had a young Robert De Niro in it) at the age of 21, Conaway was on the Broadway stage a early as 2 years old.

He would land a few guest roles after "Jennifer On My Mind" in shows such as "Happy Days," "Mary Tyler Moore" and "Barnaby Jones." But he would get his big break in 1978 when he starred opposite John Travolta and Olivia Newton-John in "Grease," playing Kenickie, one of the Burger Palace Boys.

Conaway then spent the next four years as Bobby Wheeler in the series "Taxi" before taking on various roles leading up to "Babylon 5."

Since then he has appeared in a variety of programs and movies, but projects that are mostly forgotten now.

Conaway has been hospitalized since May 11, and was apparently unconscious for at least eight hours before he was found, according to CNN.

Drew Pinsky, the host of "Celebrity Rehab," told his Twitter followers that he visited Conaway in the hospital Friday night, and was confident he would recover. He added that this was not an overdose "like the press is alleging, and certainly not dead."

The coma Conaway is in is medically induced, mostly because he is on a ventilator for the pneumonia.

Although pneumonia is a dangerous condition to have, chances of survival increase with immediate medical care. However, the sepsis Conaway is suffering from could provide some complications and lessen his chances.

His manager, Phil Brock, maintains that drugs were involved, but is hoping for the best.

"He's a really wonderful soul, a very kind and wonderful person," Brock told CNN.