“ConclusionsWe conclude that a single oral dose of pure menthol (100 mg) delays caffeine absorption and blunts the heart-rate slowing effect of caffeine, but does not affect caffeine metabolism.”
“ResultsCo-administration of menthol resulted in an increase of caffeine tmax values from 43.6±20.6 min (mean±SD) to 76.4±28.0 min (P<0.05).”
“The Cmax values of caffeine were lower in the menthol phase than in the placebo phase, but this effect was not statistically significant (P=0.06).”