An evaluation of the extraction of pharmacological markers (kavalactones) of the plant species Piper methysticum (kava-kava) was conducted. Capsules containing ground kava-kava were submitted to an in vitro method using a controlled dissolution system where the extractive mediums were a solution of 0.1M HCl, phosphate buffered solution (pH = 6.8) and distilled water, at 30 and 60 min, and in vivo that was based on the pylorus ligation method in rats. In the in vitro system starting from 6 capsules (3 g) containing the kava-kava powder, the following extractive concentrations of kavalactones were obtained: HCl (30 min.) = 0.93% (27.9 mg), HCl (60 min.) = 1.1% (33 mg), buff. (30 min) = 2.8% (84 mg), buff. (60 min.) = 0.7% (21 mg), water (30 min.) = 0.71% (21.3 mg) and water (60 min.) = 2.6% (78 mg), while in the in vivo method, 1 and 2 h after administration of 500 mg of the kava-kava powder through gavage, the extractive concentrations of total kavalactones were: 1h = 1.31% (6.55 mg) and 2h = 1.41 % (7.05 mg). In the in vitro system a slight difference was observed among the solutions, which were not statistically significant, and the same occurred with the in vivo experiment, although at the time of 2 h after administration it proved more effective in the extraction of kavalactones by the gastric juice, but below the dose recommended for therapeutic use.Colegio de Farmacéuticos de la Provincia de Buenos Aires