The 62-year-old actor - who has two daughters, Delilah, 27, and Amelia, 24, with husband Harry Hamlin - told how people thought she was "just drunk" because of her behaviour at the bash but she underwent a drug test afterwards that came back positive for various substances.
Speaking on Good Day New York, Rinna said: "I had fentanyl in my system - I'm not kidding.
"I had fentanyl, high levels of amphetamines and other things. But I can't talk a lot about it because we're still dealing with it. It was leaked, and my team is dealing with it now."
"Luckily, my husband was there and was able to get me out of there quickly," she said of husband Harry Hamlin.Â
"Because I saw other things like, 'Oh, Lisa was just drunk.' But no."
Rinna insisted she would not name who she believed to be responsible but alleged it occurred at West Hollywood bar The Abbey, where the party was held, and claimed "so many people that I know have had this happen" at the venue, including her daughters' friends.
The Abbey confirmed they were aware of Real Housewives of Beverly Hills star Rinna's claims but had found "no evidence" of anything suspicious happening.
They told People magazine in a statement: "Lisa's team shared concerns with us following her visit, and we immediately conducted a thorough internal review.
"When she became unwell, our security team assisted her and escorted her safely out of the venue. We pulled and reviewed all available surveillance footage from the time in question and interviewed staff on duty. We found no evidence of drink tampering or suspicious behaviour toward her.
"We cannot speak to medical findings and do not want to speculate about toxicology results.
"We take any report of a guest feeling unwell or unsafe extremely seriously and follow established investigative protocols."
"The Abbey has extensive surveillance coverage, trained security personnel, and ongoing drink-safety measures in place. Guest safety remains our highest priority."
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