While numerous well-designed medical studies have shown that alcohol in moderation (especially red wine) has health benefits, the general affect on sexual performance is not good.  As Shakespeare wrote in Macbeth, ” Drink (alcohol) is a provoker of three things: nose painting, sleep, and urine.  It provokes, and unprovokes: it provokes the desire, but it takes away the performance.”  While it is generally safe to use the ED medications with moderate alcohol intake, the effectiveness of the medications is greater when alcohol is avoided for a few hours before using an ED med.  Also, chronic moderate or heavy alcohol use is probably one of the main causes, along with smoking, of ED in the first place.