Piperine, the main alkaloid of black pepper, involves to activity of liver enzymes, including CYP1A2. Caffeine is primarily metabolized by this enzyme, so that the Saliva concentration of the drug is a criterion of CYP1A2 activity. Healthy volunteers are recruited. The main inclusion criteria are general health status, age between 18 to 35, no taking of enzyme inhibitor or inducer drugs and food enriched of black pepper as additive. And exclusion criteria are each chronic or metabolic disorders, and taking enzyme inhibitors and inducers. Crossover study to be carried out with one month period as wash out time. Healthy volunteer regardless gender, are randomly divided into two control and piperine receiving groups (n=20). The subject will receive placebo or piperine (1 capsule daily for 3 days before Caffeine) and Caffeine (10 mg as an oral single dose on fourth day of the study. Total period of the study is 4 days. Blood samples will be taken at 0, 0.5, 2.5 and 5 hr after Caffeine administration. The Caffeine Saliva concentration will be assayed using HPLC method. Pharmacokinetic parameters such as Saliva concentrations, clearance, half-life and volume of distribution of Caffeine in the placebo will be compared with the findings of piperine group.