The study is designed to look at the usefulness and safety of an oxybate mixed-salts oral solution or placebo for treatment of Idiopathic Hypersomnia. Idiopathic Hypersomnia (IH) is a sleep disorder in which a person is excessively sleepy during the day and has great difficulty being awakened from sleep. Study staff nor participants will know if they are receiving study drug or placebo. Participants will be male or female subjects 18-70 years old with a diagnosis of Idiopathic Hypersomnia (IH) within the last five years, and not due to other medical conditions such as Narcolepsy, restless leg syndrome, and uncontrolled hypothyroidism. A minimum of 140 study subjects will be randomized across all sites with 72 randomized to the study drug and 72 to the placebo drug. The study treatment period from screening to follow-up will last approximately 42 weeks, requiring nine visits. An overnight stay might be required to confirm the diagnosis of IH.

Candidates for this study may or may not report disturbances in odor perception as their primary reason for seeking treatment at MUSC. This study is designed to collect long term, observational data from patients who are being treated with routine clinical care in health clinics at MUSC. Data from clinical questionnaires will be de-identified and stored in a database.

The Sleep Research Data Repository (SRDR) aimed to systematically collect, analyze and store for future research sleep and sleep disorders related biological and psychological information. It will include sleep physiological measurements and the results of interviews, questionnaires, and laboratory tests. The SRDR will contain sleep related information obtained from healthy subjects and patients with psychiatric, substance abuse, neurological disorders, or any medical conditions associated with sleep disturbances. SRDR data will be made available to current and future IRB-approved investigators associated with this protocol.