 For all cohorts, subjects will be admitted to the clinic 2 days prior to beginning any dosing, and will remain in the clinic through Day 21. Blood collection for hematology, chemistry and serology analysis will be drawn at screening, and intermittently for safety assessments during the study period. Subjects in Cohorts 1-3 will have a PK sample collected pre-dose and serial PK collection post-dosing. Subjects in Cohort 4 will have daily PK collections while admitted during Suboxone dosing and serially after RBP-6000 administration. 