The Brazilian scientists behind the research say that while the energy drink can lessen the headache, weakness and dry mouth usually associated with alcohol, it cannot significantly reduce the effect alcohol has on motor coordination and visual reaction time.
The research is pertinent as the combined use of alcohol and energy drinks such as Red Bull have become increasingly popular among young adults in recent years.
In the UK for example, the continued popularity of energy drinks has boosted the sector's value to over £1 billion. One reason is that energy drinks command a substantial premium over other soft drinks.
According to Mintel, consumers are prepared to pay a relatively high price per litre for single-serve units for the convenience and energy boost. Some £12 million was spent on advertising energy and stimulant drinks above the line in 2004, according to Nielsen Media Research, 95 per cent of which was invested by Red Bull and GSK (Lucozade).
Users often report reduced sleepiness and increased sensations of pleasure. But this new study shows a considerable disconnection between subjects' perceptions and objective measures of their abilities.
Although combined use reduces the sensation of tiredness and sleepiness, actual capabilities are significantly impaired.
"In Brazil, as in other countries, young people believe that Red Bull and other energy drinks avoid the sleepiness caused by alcoholic beverages and increase their capacity to dance all night," said Maria Lucia O. Souza-Formigoni, associate professor in the department of psychobiology at the Federal University of São Paulo in Brazil and corresponding author for the study.
"There are two key points. Although combined ingestion decreases the sensation of tiredness and sleepiness, objective measures of motor coordination showed that it cannot reduce the harmful effects of alcohol on motor coordination.
"In other words, the person is drunk but does not feel as drunk as he really is.
"The second important point is that many users reported using energy drinks to reduce a not-so-pleasant taste of alcoholic beverages, which could dangerously increase the amount - as well as the speed of ingestion - of alcoholic beverages."
Souza-Formigoni said there was a need for further studies to test higher doses of both alcohol and energy drinks.
"We are also testing separately the different substances of energy drinks - caffeine, taurine, etc - in combination with alcohol to determine which of them are responsible for [for what effects during] interaction."
This research appeared in Alcoholism: Clinical & Experimental Research (ACER) , which is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism.
Co-authors of the ACER paper, Effects of Energy Drink Ingestion on Alcohol Intoxication, were Sionaldo Eduardo Ferreira, Marco Túlio de Mello, and Maria Lucia Oliveira de Souza-Formigoni of the department of psychobiology at the Federal University of São Paulo, Brazil.