On day 1 of the study, study subjects will take one dose each of caffeine and dextromethorphan at 4:00 P.M.. They will empty their bladder before the dosing and then collect all their urine after the dosing for the rest of the day and including the next mornings first urine. They will bring the urine samples to the Clinical Center when the collection is complete. This procedure will be repeated 1 week later (study day 8). After the second urine collection is completed, subjects will take 200 milligrams of kava 3 times a day for 21 days. On study day 29 (after 21 days of kava), subjects will repeat the dextromethorphan and caffeine dosing and urine collection described above, while continuing to take kava.