 Subjects will be asked to sign the informed consent form at the screening visit. If eligible and willing to participate, subjects will enter into the study. Subjects will be required to attend the research unit on eight separate occasions during the study, in addition to the screening visit. Treatment Period 1 requires the subject to attend the unit for two consecutive overnight stays Day -1 and Day 1, after which subjects will be discharged from the unit on Day 2 following the 24 hr post-dose PK blood sample. Subjects will then be required to return to the unit for PK blood samples to be obtained on Day 3 48 hr post-dose, Day 4 72 hr post-dose and Day 8 168 hr post-dose. Following a washout period of seven days, subjects will be required to attend the unit for Treatment Period 2, which will involve eight consecutive overnight stays Days 14 to 21, after which subjects will be discharged from the unit on Day 22 following the 24 hr post-dose PK blood sample. Subjects will then be required to return to the unit for PK blood samples to be obtained on Day 23 48 hr post-dose, Day 24 72 hr post-dose and Day 28 168 hr post-dose. 