Both caffeine and pseudoephedrine are recognised to be central nervous system stimulants but during competition, caffeine is a permitted substance, whereas pseudoephedrine is a banned substance.
A new study, published in International Journal of Sport Nutrition and Exercise Metabolism not only confirmed the performance-enhancing benefits of caffeine (CAF), but showed that it is actually more effective than an illegal dose of pseudoephedrine (PSE).
The study compared the effect of caffeine and pseudoephedrine use on cycling time trial performance to explore whether the legal stimulant was any less ergogenic than the banned substance and found the opposite was the case.
Ironically it also shows that athletes banned for PSE misuse may not have incurred a performance gain any better than that achievable via legal means.
Read Caffeine for Sports Performance for more on this subject.