Cocaine has been a very central part of gaming with it becoming a very controversial subject when it comes to game politics. Ratings boards are often quite skittish about graphic depictions of drug use, and will often allow it to be referenced, but not explicitly shown. This is demonstrated by the myriad of scenes in GTA IV where a character will be seen bending down and sniffing something out of shot- a clear case of a reference to cocaine without an actual visual depiction in order to appease the politics of the system.
In Alpha Protocol Konstantin Brayko will actively snort cocaine residue from his knife during a boss fight in order to enter a drug fueled rage. Although it is not explicitly shown, it is heavily implied. After the boss fight Brayko's knife will be present in Michael Thorton's safehouse and when examined Michael will say, "I think there's enough coke residue on this knife to get very, very high."