Normal healthy volunteers between 18 and 55 years of age may be eligible for this study. Candidates are screened with a medical history, physical examination, and blood and urine tests, including a blood test for analysis of genes that control and regulate UGTs. Pregnant women and nursing mothers are excluded from the study. Women who are able to have a child and men who can father a child must either abstain from sex or use two reliable forms of birth control during the study and for 3 months after its completion.