If you are in this study, you will be placed in one of two study groups: one group will receive the study drug and one will receive a placebo. You will be assigned a study group by chance using a process similar to the flip of a coin. This process is called randomization. Neither you nor the study staff will select the group you will be in. A placebo looks like the study drug but is an inactive substance that has no medication. Researchers use a placebo to see if the study drug works better or is safer than not taking anything. You will have a 66% chance of getting the study drug. You will receive placebo at some point during the study but you will not know whether you are receiving placebo or study drug during the entire study. However, if you have a medical emergency, the investigators can get this information.