In a sneak-peek clip of Diane Sawyer‘s interview with Matthew Perry, set to air on ABC Friday (October 28th), the Friends star opened up about his struggle with addiction—which he also details in his forthcoming memoir Friends, Lovers, and the Big Terrible Thing. Perry told Sawyer that he’s especially thankful for Jennifer Aniston‘s support.

As Friends reached the top of the charts, Perry said he was deep in the throes of addiction. “At the time I should have been the toast of the town.” Instead, he shared, “I was in a dark room meeting nothing but drug dealers and completely alone.”

The Fools Rush In actor revealed that he was taking “55 Vicodin a day,” when Sawyer mentioned “methadone, Xanax, full quart of vodka” as his drugs of choice. He also shared that he was “really grateful” for Jennifer Aniston confronting him. “We know you’re drinking,” she said to him at one point—a moment he labeled as “scary.”

“She was the one that reached out the most,” he told Sawyer. “I'm really grateful to her for that.”