The `Bounty Hunter` star is currently at the Betty Ford Center in California, where he is receiving treatment for substance abuse.
According to TMZ.com, Gerard entered the facility three weeks ago after realising he was becoming dependent on prescription drugs.
His problems were allegedly triggered by the physical demands of shooting `300` in 2006 when he started taking painkillers to cope with numerous injuries he got while shooting the action film.
The problem got worse when the 42-year-old actor was filming `Of Men and Mavericks` when he was badly hurt in December during a surfing accident.
In December, the Scottish star was said to have cheated death by seconds during his surfing accident, which saw him trapped underwater after being hit by a series of waves.
Gerard got caught in a 12ft swell while filming `Of Men and Mavericks` - which tells the true life story of late surfing icon Jay Moriarty - at the infamous big-wave Northern Californian surfing spot Maverick`s.
After being pulled from the water onto a jet ski, he was taken to shore and driven to Stanford Medical Center where he was kept under observation for one night.