The Situation has confirmed that he recently entered a treatment programme for a "prescription medication problem".
Pivarnick previously starred alongside Sorrentino on Jersey Shore before quitting the show after the second season.
She has now told the New York Post that he was like "Popeye on crack" during filming.
"When he was on the show, he got in trouble for having prescription pills," she claimed. "We were filming in a club in Miami... one of the producers said, 'Hey, what was that?' He had to give them up."
Recent reports have alleged that The Situation was also treated for alcohol abuse.
A spokesperson for MTV has previously said that it "fully expects" Sorrentino to return for Jersey Shore's upcoming sixth season.