Schreiber was chief executive at Canada's largest pharmacy chain for four years until 2011, before it was acquired by Loblaws (TSX:L).
Rexall Health will include the Rexall/Rexall Pharma Plus pharmacy chain, which has more than 460 locations in every province except Quebec.
It also includes the Medicentres family health-care clinics in Edmonton, Calgary, and London and Windsor, Ont., and Claimsecure Inc., which provides health benefit claims management to Canadian corporations.
Katz Group founder and chairman Daryl Katz said Schreiber has been a consultant to its health-related businesses for two years.
Analyst Irene Nattel of RBC Capital Markets said Schreiber is experienced but Shoppers should continue to enjoy an advantage from its substantial scale and market presence.
Also on HuffPost