The issued patents are licensed exclusively to Pain Therapeutics in the US and international markets with regards to four opioid drugs.
Pain Therapeutics CEO and president Remi Barbier said, "We believe these four issued patents can provide additional intellectual property protection for REMOXY until 2025 or beyond."
The patents are the outcome of combined work done by both Pain Therapeutics and Durect.
Remoxy was issued two patents in Europe, which expire in 2016 and 2023, respectively, as well as any eligible patent term extensions, the company said.