Pangar was once ruled over by the Goa'uld Shak'ran before the planet was taken from him by Ra. After a struggle with one of Ra's Enemies the planet was lost to him but not before his former Queen Egeria, the mother of the Tok'ra was imprisoned on the planet.
After the Goa'uld left the planet the Pangarans developed into a fairly advanced industrial civilization. The Pangarans later found Ra's former outpost and unearthed a symbiote queen in an archaeological dig. They discovered that her off-spring could be used to create a drug that had amazing healing powers which they experimented on and were able to create Tretonin.
By the time they were visited by SG-1, quite a large portion of the planets population was already using Tretonin, but the Queen was dying and unable to produce healthy offspring to use to make Tretonin, which was the only thing keeping them healthy. The Pangarans offered Earth Tretonin in return for gate addresses to Goa'uld-occupied worlds, in the effort of retrieving a queen to make more Tretonin. Ultimately, however, SG-1 discovered that the Queen the Pangarans have been using is in fact the mother of the Tok'ra. The Tok'ra were unable to save her, but not before she tells them that she is proud of them. The Tok'ra are later able to produce a viable means of restoring the immune systems of those taking Tretonin, and save many Pangaran lives. (SG1: "Cure")