INFLUENCE OF GENDER ON THE PLASMA CONCENTRATION OF CAFFEINE AND ITS METABOLITES AFTER BODY WEIGHT-DEPENDENT DOSING

Background
Caffeine is a widely consumed central nervous system stimulant, but its optimal dosing remains uncertain. This study examines gender-specific plasma caffeine and metabolite levels following weight-adjusted dosing.

Material and methods
The study included 38 women and 19 men (age 26.2±3.2; BMI 23.9±4.5). Participants received 6 mg of caffeine per kilogram of body weight, resulting in mean absolute doses of 398.8±91.9 mg for women and 485.8±86.2 mg for men. Blood samples were collected 60 minutes post-caffeine ingestion, and plasma concentrations of caffeine and its metabolites were analyzed using high-performance liquid chromatography.

Results
A Mann-Whitney U test revealed statistically significant differences in caffeine dosage between the study groups (U=144, p<0.001, r=0.49). The analysis of the caffeine concentration variable showed statistically significant differences between the study groups (U=244.5, p=0.049, r=0.26).

Conclusions
Although women received significantly smaller total doses of caffeine, they exhibited significantly higher plasma concentrations of caffeine than men. No significant differences were observed in the concentrations of paraxanthine or theobromine, while theophylline was undetectable in any of the samples. These findings underscore gender-specific differences in caffeine metabolism and highlight the potential need for tailored caffeine dosing based on gender.