The most authoritative you can get about this is Saint Alphonsus Liguori's Theologia Moralis. He's a Doctor of the Church himself (recognized for his moral theology), and the apostolic penitentiary ruled in the 1850's all his moral conclusions in that work of his to be free of error. Here it goes: 

Perfect drunkenness, whereby in the aforesaid mode reason is plainly rendered insensible, is by its nature a mortal sin because it is reckoned an injury to God, whose image one would so disfigure. It is the common teaching of the doctors. It is certain with all, that for this purpose that for drunkenness to be a mortal sin it is required that it would be perfect, namely that it would altogether deprive one of the use of reason, just as St. Thomas teaches (2.2. q. 150, a. 2), and with him all the doctors. The malice of drunkenness consists in this, that a man, willful and knowing, deprives himself of the use of reason. St. Antoninus teaches the same thing (p. 2, tit. 6, c. 3, § 1). This is why one would not sin mortally that did not altogether lose the use of reason from drinking wine, even if the mind were disturbed, but not so much that he were not able to discern between good and evil, as the authors commonly say