Dr. Khristine Eroshevich, a Los Angeles psychiatrist and friend of the former Playboy Playmate, is under investigation, board spokeswoman Candis Cohen said.
Cohen declined to provide other details.
On Wednesday, Cohen would not comment on a possible investigation, saying such information was not public record.
According to documents from the medical examiner's office in Florida, Eroshevich authorized all the prescription medications in the Florida hotel room where Smith was found unresponsive shortly before her death on Feb. 8.
Eroshevich had traveled with Smith to Florida.
More than 600 pills, including 450 muscle relaxants, were missing from prescriptions that were no more than five weeks old, according to the documents, which were obtained by The Associated Press through a public records request.