This trial is testing a drug for adult subjects with sleep apnea to see if it can help treat excessive sleepiness and improve patients’ ability to stay awake. We are looking for subjects who have been diagnosed with sleep apnea and are either currently being treated for sleep apnea, or have tried treatment in the past (either with CPAP, oral appliance, or surgery). Subjects do not need to be currently treated for sleep apnea. Subjects will undergo overnight sleep studies and daytime sleepiness tests to determine level of sleepiness. If subjects qualify for the study, they will be given the study medication and will take it for up to 6 weeks. Subjects will be asked to come in for periodic monitoring visits to assess changes in sleepiness (including overnight sleep studies and daytime sleepiness tests). All tests are covered by the sponsor (no tests are billed to insurance) and compensation is provided for time and travel for the study.