 - Females of childbearing potential must have a negative urine pregnancy test upon admission and agree to avoid pregnancy throughout the course of the study. Since this population is hospitalized for the duration of the study, an agreement of sexual abstinence is appropriate for this trial. Those subjects who do not wish to commit to sexual abstinence for the duration of this study must agree to avoid pregnancy by using a medically supervised method of contraception such as hormonal contraception in conjunction with a vaginal spermicide or a tubal ligation at least 3 months prior to study entry 