I have written about the effects of Red Bull and alcohol , but I just read a excellent post by Lawrence Taylor who writes the DUI Blog.here is an excerpt from his post on the effects of caffeine and alcohol
Caffeine and alcohol have a synergistic effect — that is, they combine to produce an accelerated effect. Rather than sobering a person up, as is commonly believed, coffee can actually increase the symptoms of alcohol.
The definitive studies were done by researchers in Great Britain and reported in an article entitled, "Interactions of Alcohol and Caffeine on Human Reaction Time", appearing in the scientific journal Aviation, Space and Environmental Medicine 528 (June 1983).
The conclusions of the scientists:
"Alcohol has always been categorized as a central depressant and caffeine as a central stimulant. Therefore, it should follow that an antagonistic [counter-active] interaction should occur when these two drugs are ingested simultaneously. But as these results illustrate, this is not necessarily the case…
"Caffeine has a synergistic interaction with alcohol…(It) has the effect of potentiating the detrimental effects already induced by alcohol….Motor skills which involve delicate muscular coordination and accurate timing have been found to be adversely affected by caffeine
This study coupled with the Wake Forrest and University of Florida studies clearly show that the caffeine use magnifies coordination problems which may effect the field sobriety tests.