Voluntarily intoxication is not a defense to a contract: the courts hold that since you chose to get drunk, you are liable for the consequences of that choice (the same way, for example, that a DUI/DWI driver can't say, "but I didn't know what I was doing because I was drunk" and escap liability). Only involuntary intoxication--being drugged; having an unxpected or unpredicted drug interaction between medicines you are taking; being given something to drink without being told what it is--might provide a defense.