"The wheels of justice grind slowly, but they grind," said Sally Finnila Sloane, whose brother Karl, 43, fatally overdosed on a cocktail of drugs in 2007, including two prescribed by Vu. "I was glad to see that somebody in charge was looking into this so it doesn't happen to anyone else."
IN DEPTH: Read the Times investigation
Charles Thurber, whose 22-year-old daughter Jennifer died of an overdose the same year, said he received a letter seeking permission to access her medical files.
She died after taking multiple drugs, including methadone and morphine prescribed by Vu, coroner's records show.
Thurber said he signed the form and sent it back to the medical board.
"It's definitely warranted," he said of the investigation.
Vu's attorney, Richard Wynn, said the doctor would cooperate fully with the investigation. He said Vu hopes that the medical board will form a committee to develop better protocols for treating chronic pain, and that he will be invited to participate.
"Dr. Vu is more than happy to assist in any way he can to make the system better," Wynn said. "We want not only to comply but to come up with a solution."
Fatal overdoses involving prescription painkillers and anti-anxiety drugs have risen sharply in the last decade, fueling a doubling of drug fatalities in the United States.
Authorities have focused on how addicts and dealers obtain such medications illegally, such as by robbing pharmacies or raiding family medicine cabinets.
A series of Times articles published last year showed that many patients overdose on medications obtained lawfully with a doctor's prescription. By studying coroners' records across Southern California, The Times identified 3,733 fatal overdoses from 2006 through 2011 and determined that nearly half stemmed from drugs prescribed for the deceased by a physician.