Anna Nicole Smith's son Daniel had at least seven drugs in his system when he died on 10 September, according to toxicology reports.
Daniel was found dead in his mother's hospital room in the Bahamas, three days after she had given birth to new daughter Dannielynn Hope.
Dr Cyril Wecht, a private pathologist hired by the Smith family, confirms to US publication People that the antidepressant Amitriptyline, as well as two over-the-counter cold medicines, were found in Daniel's body, along with methadone and the antidepressants Lexapro and Zoloft.
Sources also tell the magazine a mild over-the-counter sedative was found in the 20-year-old's system.
Wecht insists the other medications played no role in Daniel's death and reiterates his assertion Daniel was killed by a combination of Lexapro, Zoloft and methadone only.
He said of the other medications: "The levels are insignificant and they don't mean a thing. They're of no consequence."