[Significance of caffeine values in serum, saliva and urine--determination of pharmacokinetic data by non-invasive methods in psychopharmacologic studies].

For psychopharmacological studies with caffeine two reliable non-invasive methods are available in order to determine pharmacokinetic parameters simultaneously with psychometric tests, without any appreciable impairment of the experimental subject. The investigation were performed in 13 healthy volunteers. Caffeine was determined in serum, saliva and urine. The caffeine level in saliva was about 70% of that in serum, corresponding to the percentage freely dissolved in serum. A good correlation was found to exist between elimination half-lives for serum and saliva levels (r = 0.9702) as well as serum and urine values (r = 0.8784). The amount of caffeine excreted in urine in its unmetabolized form was 1.1 +/- 0.2% of the dose administered. Furthermore, the saliva level was seen to represent the serum level on a broad scale. Sixty minutes after oral uptake, saliva levels were falsified due to adsorption of caffeine to the buccal mucosa. The special pattern of the saliva level during the phases of absorption and distribution is discussed.