Ahmanson spokesman Ken Werther told the Los Angeles Times the 67-year-old actor is expected to rejoin the touring production of the stage drama Friday, following a six-day hospitalization.
Keach plays former U.S. President Richard Nixon in the show, which is to wrap up its run at the Ahmanson Sunday.
Bob Ari, Keach's understudy in the play, took over the role March 17 when Keach fell ill. Ari will play the role of Nixon until Thursday and also for matinee performances Saturday and Sunday, so Keach doesn't have to do two shows a day, the Times said.
Keach's Broadway credits include "Danton's Death," "The Country Wife," "The Caucasian Chalk Circle," "King Lear," "Indians," "Deathtrap," "Solitary Confinement" and "The Kentucky Cycle." He won a Golden Globe Award for his portrayal of the titular scribe in the TV miniseries "Hemingway," and played fictional private detective Mike Hammer on a television series and in several TV movies.