In short, "Stimulants out! 'Supplements' in!", as the developer on its Facebook page.
The offending drugs featured both legal and illicit substances including methadone, morphine, amphetamines, stimulants, acetaminophen, ibuprofen, codeine, aspirin, "trucker pills", painkillers, and tussin.
The developer also stated that State of Decay will be on Steam but "not soon".
State of Decay was released on the 5th June 2013, and became the XBLA game.