Inclusion Criteria:

• Male or female subjects 16 years of age or older.
• Willing and able to give written informed consent for study participation. For young adults (16 and 17 years old) who have not reached the age of majority they must be capable of giving assent and consent from a legally authorized guardian must be obtained, as required by local laws and regulations.
• Documented evidence of a diagnosis of NT1 or NT2 as, in part, determined by an overnight PSG and next-day MSLT with 2 or more SOREMPs with mean sleep latency in the pathological range i.e. < 8 minutes and meeting the NT1 and NT2 as defined by the International Classification of Sleep Disorders -3 criteria.
• Current continuing presence of EDS as defined by subject report for the last 3 months and an ESS > 10.
• For NT1 only, current continuing presence of cataplexy as defined by subject report for the last 3 months.
• Subjects may use concomitant stimulants, but must comply with the following:
  • They must be on a stable dose of stimulants for at least 3 weeks prior to starting the screening process for this study; AND
  • They must use the same stimulant regimen throughout the entire study period, including during screening and posttreatment periods;
  • They must discontinue all anti-cataplexy drugs.
• Addition inclusion criteria per protocol.

Exclusion Criteria:

• Prior use of sodium oxybate is allowed in the study but with the following exclusions:
  • a. Previous dosing must have been limited to no more than 4.5g per night;
  • b. Patient should not have taken sodium oxybate for more than 2 weeks;
  • c. All previous dosing must not have occurred within the last year prior to entry to the study.
• Current use of sodium valproate.
• Any use of the following prohibited medications for the duration of the clinical study:
  • Anticonvulsants;
  • Clonidine;
  • SSRIs and serotonin and norepinephrine re-uptake inhibitors (SNRIs);
  • MAOIs;
  • TCAs;
  • Hypnotics;
  • Anxiolytics;
  • Sedating antihistamines;
  • Antipsychotics;
  • Other experimental medications designed to treat narcolepsy, cataplexy or any other condition.
• Treatment with any investigational products within 3 months before study enrollment.
• Any drug known to affect sleep-wake function. Concomitant stimulant use is permitted.
• A diagnosis of sleep apnea or any other sleep disorder known to cause EDS as determined by PSG and sleep history, including any PSG results indicating an apnea-hypopnea index (AHI) ≥ 15.
• The presence of any unstable or clinically significant medical and psychiatric disorders (as determined by medical or psychiatric history, physical examination, and/or clinical laboratory test) which in the opinion of the investigator may either put the subject at risk by participation in the study, or may influence the results of the study.
• Subjects with a previous history or current ideation of suicide attempt.
• Subjects who have a history of drug or alcohol use that, in the opinion of the investigator would interfere with study subject safety and adherence to study requirements.
• Required commercial or equivalent driving during the study period.
• An occupation that requires variable shift work or routine night shifts.
• Any travel across more than 3 time zones during the course of the study.
• Consuming more than 14 standard alcoholic drinks per week, on average, before participating in the clinical research study.
• Smoking during the night (approximately between 9 pm and 7 am) during the course of the study.
• Female subjects who are lactating or have a positive pregnancy test. Females of reproductive potential not willing or able to employ effective methods of birth control/contraception to prevent pregnancy for the duration of the study and for up to 1 week after completing study treatment.
• Any current malignancy and/or any history of malignancy within last 3 years.
• A history of seizure disorder, head trauma, or past invasive intracranial surgery.
• Subjects with severe chronic obstructive pulmonary disease. Subjects with mild to moderate chronic obstructive pulmonary disease and assessed as stable by the principal investigator (PI) are eligible.
• Principal investigator judgement on other underlying respiratory and/or other underlying condition or disorder that would potentiate risk of respiratory or CNS depression with concomitant use of sodium oxybate.
• Known hepatitis B surface antigen-positive status or known or suspected active hepatitis C infection.
• Known human immunodeficiency virus infection or acquired immunodeficiency syndrome related illness.
• Scheduled for procedures requiring general anesthesia during the study.
• Known contraindication/allergy/sensitivity/intolerance to the study drug, sodium oxybate, or the inactive ingredients of FT218 or placebo.
• Atrial fibrillation or an abnormal electrocardioelectrocardiogram (ECG) demonstrating clinically significant dysrhythmia(s).
• Recent myocardial infarction or coronary revascularization (less than 3 months).
• Uncontrolled hypertension.
• Known succinic semi-aldehyde dehydrogenase deficiency.
  • Moderately or severely altered blood chemistry as defined by any one of the following:
    • A Cockcroft-Gault calculated creatinine clearance < 60 mL/min; OR
    • Liver function tests more than twice the upper limit of normal; OR
    • Serum bilirubin more than 1.5 times the upper limit of normal.