The True Lies star, who himself battled substance abuse for years, staged an intervention last month (30Dec09) to convince Jason Davis to enter a treatment program to kick his own addictions.
Davis is believed to have left the centre a day later, on New Year's Eve (31Dec09), and was upset Arnold had coerced him into the stint.
According to RadarOnline.com, Davis then overdosed on an unknown drug and was checked into Los Angeles' Cedars-Sinai Medical Center.
A source tells the website, "Jason was furious about the intervention. He wants to be left alone so he can do what he wants to."