The stunt will also involve the deployment of an army of Eminem look-a-likes across London's West End and has been devised to publicise the release of the album, which the rapper started writing while he was in rehab fighting his addiction to drugs.
The event will tap into the current wave of publicity surrounding the album release, making a tongue-in-cheek counterpoint to this week's tabloid stories about how Elton John's advice helped Eminem fight his addiction.
The Relapse Rehab Centre will open at 9am on Monday 18 May, the day the album is released, and will close at 8pm on the same day.
Giant letter Es and the Eminem look-a-likes will mark the centre's whereabouts (North Piazza, Covent Garden), which Blazinstar hopes will attract visitors and generate word-of-mouth.
Shaz Smilansky, Blazinstar's marketing director, said: "The Eminem Relapse Rehab Centre is designed to bring the 'Relapse' album's rehab message to life."
Blazinstar was briefed to work on the project by MediaCom, whose client is Universal Polydor. SuperSonic PR is also working on the integrated communications campaign.
This week press reports covered Eminem's admission that confiding in Elton John had helped him get off drugs.
In an interview with the Detroit Metro Times, Eminem said: "Me and him have similar lives and stuff.
"We became friends and I talk to him about things, career-wise."
The friendship between the rapper and the singer stems back to the 2001 Grammy Awards, when Elton John joined onstage with Eminem to perform a version of the latter's 'Stan'.
The rap star was at the time facing accusations of homophobia, but Elton John had surprised many by coming to his defence.