The recent merger of Catamaran into UnitedHealth Group , followed by this week's acquisition of Omnicare by CVS Health , has placed a spotlight on the Pharmacy Benefit Manager space and put pressure on Walgreens Boots Alliance to follow suit and buy its own PBM. Ironically, Walgreens actually got out of the PBM market in 2011, selling its unit to a company called Catalyst, which eventually became part of Catamaran.