When the error was discovered, Watson said, a nursing supervisor told him: "I want you to sign this paper saying that this had happened, but it had no effect on you." He said he signed the paper, even though he wasn't sure it was true, "because I didn't know what I was doing."
The error comes even as officials at the hospital and the Los Angeles County health department, which owns the facility, have been assuring regulators that they have fixed problems there.
The hospital is under close scrutiny by state and federal inspectors because of a pattern of lapses in care, including the deaths of five patients last year after a host of errors by nurses and other employees.
County and hospital officials have stressed that paid consultants and a team of top health department managers are on-site at King/Drew, which is in Willowbrook, just south of Watts, to ensure nothing further goes wrong.
After learning of the latest patient-care blunder, county Supervisor Gloria Molina said employees needed to be held accountable.
"It's caught up to them now," she said. "They're just not prepared to meet the mission out there, and they're going to have to move out of the way."
Supervisor Zev Yaroslavsky said that he was running out of ways to express his outrage and frustration that patients continued to be harmed at King/Drew.
"You can't argue that this is an anomaly," he said. "It appears to be more normal than an anomaly."
Supervisor Yvonne Brathwaite Burke, whose district includes the hospital, expressed anger. But she said she believed that "considerable work" had been done to correct problems at King/Drew.
"I don't know that you can correct all of the problems from 25 years in three months," she said. "It's going to take awhile because there's still a lot of people there that have to be removed and there has to be a whole discipline approach -- so that when people do something, it has to be in their records so you can hold them accountable. And that has not been done there."
Physicians who study how and why medical mistakes occur said the current situation at King/Drew makes it ripe for errors. A hospital in turmoil faces more problems preventing errors because it is making so many changes that require learning new systems and procedures, said Dr. Robert M. Wachter, chief of the medical service at UC San Francisco Medical Center and author of a new book on medical mistakes.
"If this particular patient is lucky enough not to be durably harmed by the Gleevec, that's just dumb luck," Wachter said, referring to the drug that Watson received.
Gleevec is one in a new generation of cancer drugs that target specific molecules. The drugs are designed to kill cancer cells while avoiding serious damage to normal cells, according to the National Cancer Institute. Gleevec was approved in 2001 for use in patients with a form of leukemia.
County health officials said they were investigating the incident and would decide later this week whether to discipline employees.
"Obviously something like this is terrible," said Fred Leaf, chief operating officer of the county Department of Health Services. "But you can believe, you can bet, that every time something occurs, the safety process doubles.... I think we're doing everything we can to assure there's a safe environment."
A health department spokesman, John Wallace, confirmed Wednesday that the incident had happened but would not confirm Watson's identity, citing privacy rules. He said officials did not yet know if the patient had suffered any harm from taking the medication.
Watson said, however, that his eyes were swollen to the size of "golf balls" and that he was unable to see out of one of them.