I see people combining the two all the time, and it has always struck me as an abuse. Not a nasty abuse, just a small one:
# Study results show that drinking alcohol and Red Bull® together significantly reduces the perception of headache, weakness, dry mouth and impairment of motor coordination.
# Red Bull® does not, however, significantly reduce alcohol-related deficits on objective measures of motor coordination and visual reaction time.
# People who combine alcohol with energy drinks may be at even greater risk for problems such as automobile accidents because they believe they are unimpaired.
Link.
