Jan. 15, 2008 -- For the first time, actor Jeremy Piven defended his sudden departure from a successful Broadway play due to mercury poisoning in an exclusive interview on "Good Morning America" today.
The "Entourage" star left a leading role in the critically praised Broadway revival of "Speed-the-Plow" less than two months after the show opened because of fatigue caused by mercury poisoning.
Piven said he was "brought to [his] knees" by his condition and said that on doctor's orders he "couldn't do it."
"The last thing I ever thought about doing was not completing this run. I've never not completed anything in my life," the Emmy-winning actor said. "They pulled me out of this thing, and that's the truth."
"You talk about 'the show must go on,' this is in my DNA. To have the rap be on me that I walked out on this thing. … This was the greatest moment of my life," he said.
Though Piven spent three days in the hospital, his claim was met with harsh skepticism by many.
"I talked to Jeremy on the phone, and he told me that he discovered that he had a very high level of mercury. So my understanding is that he is leaving show business to pursue a career as a thermometer," "Speed-the-Plow" playwright David Mamet told Daily Variety in December when Piven's departure was announced.
"He's a brilliant playwright and that's a great line," a smiling Piven said today. "It's a very funny line."
But Piven said the effects of the poisoning were nothing to joke about.
"It progressed to the point where that final Sunday I was having problems spatially," he said. The actor said that he had trouble remembering his lines and maintaining his balance and that he was suffering from extreme fatigue.
"You have to understand, I'm not a doctor and I don't even play one on TV," Piven said. "I can only speak of how this was playing on me."
After three days in the hospital, Piven said a cardiologist ordered him to leave the show for "forced rest."
"He said, 'You have a resting heart rate of 47. Your body is trying to keep up,'" Piven said.
Before the actor left, The New York Times called his turn in "Speed-the-Plow" one of "uncanny grace and intelligence." He admitted to strong regrets.
"I was living my dream," he said. "We had brilliant reviews. We were sold out every night. This was the greatest time of my life. I would have loved to go out. I couldn't do it."
High Mercury Levels: Sushi to Blame?
Dr. Carlon Colker, the primary internist treating the "Entourage" actor, detailed his debilitating condition.
"This is a situation of mercury toxicity," Colker, the medical director of Peak Wellness of Greenwich, Conn., told ABCNews.com. "His level [of mercury] was quite high, almost six times the normal limit. … In this case, it's either because of fish -- he ate sushi twice a day for years -- or because of the Chinese herbs he was taking, or both. We're pretty sure about the fish. How much the Chinese herbs contributed, we don't know. We don't have the specifics of which herbs he took."
Piven told "GMA" today that fish was his only source of protein for the last 20 years. Piven said he hasn't had a morsel of fish in five months.
"He'll be OK. I think it'll take a few weeks to a couple of months," Colker said. "Unfortunately it was like pulling teeth to get him out of the show. This is a situation that I think will resolve as long as he's attending to his health."
Piven's abrupt departure from "Speed-the-Plow" was a move deserving of its own "Entourage" episode for all the rumblings it caused, but a statement by the show's producers lacked drama.
"We have been advised by Jeremy Piven's medical representatives that he is seriously ill and is unable to fulfill his contractual obligation to 'Speed-the-Plow.' Consequently, he has left the production 10 weeks early," the statement to ABCNews.com said.
According to the U.S. Environmental Protection Agency, the most common way people ingest mercury is by eating fish containing methylmercury -- most often tuna or swordfish -- or by breaking products containing elemental mercury, such as a thermometer.
Mercury is one of the most dangerous toxins on Earth. The amount of damage it can do to a person depends on when the person is exposed (as a fetus, child or adult), the type of exposure (whether it's swallowed, touched or inhaled) and the length of the exposure.
At its worst, inhaled mercury can cause brain damage or death. Swallowing mercury can cause permanent kidney damage or death. However, according to the University of Maryland Medical Center, most exposure to mercury builds up over periods of years. In that case, mercury poisoning can cause numbness, tremors, blindness and memory problems.
Mercury poisoning treatment can last for months and usually consists of extended use of "chealator" drugs which help remove heavy metals from the body, according to the University of Maryland Medical Center.
Piven's 'Speed-the-Plow' Part to Be Picked Up by Macy, Butz
Two actors have filled in for Piven since his departure.
Tony Award winner Norbert Leo Butz took on the part in December and early January. Academy Award nominee William H. Macy took up the reins Tuesday.
In September, Piven picked up his third consecutive Emmy for his work on "Entourage" and, in his acceptance speech, alluded to the fact that small-screen acting talent doesn't necessarily translate to the stage, perhaps foreshadowing his abrupt departure from "Speed-the-Plow."
"I just got off a plane from New York in which I'm doing a play," Piven said. "And what's so interesting is that I'm in the midst of this rehearsal and I'm feeling like maybe I should go into roofing, I'm so bad. That's what it feels like right now."
The Associated Press contributed to this story. Additional reporting contributed by Lauren Cox.