This study will assess safety and tolerability when taking GSK189075 at doses that are likely to be higher than the expected prescribed doses. The study will also measure the level of GSK189075 in blood after dosing as well as the effect of the drug on certain laboratory tests performed on volunteer urine and blood. Each volunteer will take part in 3 dosing periods and will be given a different dose level at each period (either 2000mg, 4000mg, or a placebo). Volunteers will not know which of the three doses they are receiving. In each period, volunteers will dose every morning for three straight days. Before and after dosing, blood pressure, heart rate, laboratory tests on blood and urine, physical examinations and ECGs will be taken to assess safety. Volunteers will also be asked to provide information should they feel they are having a possible effect from the GSK189075. The levels of GSK189075 in the blood will be assessed by multiple blood draws, most of these will follow the third dose in each period. Depending on the results from the preceding periods, a fourth period may be added to the study to assess another dose level. The fourth period, if this is to occur, will be the same design as the other three periods, and the dose received will be less than 4000mg.