Brown, 27, is a former fourth-round pick of the Kansas City Chiefs. He spent close to three years with the team before he was placed on waivers and later claimed by the Dolphins in December of last year.
He has appeared in two games this season, but has yet to record a single statistic.
Purifoy, 21, was a priority undrafted free agent signing of the Colts. He has appeared in 11 games this season and recorded seven tackles, a forced fumble and a pass defense. Pro Football Focus has him down for playing 48 snaps this season.
There is a good chance that he’ll end up on the Colts’ practice squad if he clears waivers.