Inclusion Criteria:

   1. Male or female subjects 16 years of age or older

   2. 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

   3. 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.

   4. Current continuing presence of EDS as defined by subject report for the last 3 months
   and an ESS > 10

   5. For NT1 only, current continuing presence of cataplexy as defined by subject report
   for the last 3 months

   6. Subjects may use concomitant stimulants, but must comply with the following:

      1. They must be on a stable dose of stimulants for at least 3 weeks prior to
      starting the screening process for this study; AND

      2. They must use the same stimulant regimen throughout the entire study period,
      including during screening and posttreatment periods

      3. They must discontinue all anti cataplexy drugs

   7. Addition inclusion criteria per protocol

Exclusion criteria

   1. Any prior use of sodium oxybate is allowed in the study but within the following
   exclusions:

      1. Previous dosing must have been limited to no more than 4.5g per night

      2. Patient should not have taken sodium oxybate for more than 2 weeks.

      3. All previous dosing must not have occurred within the last year prior to entry to
      the study.

   2. Current use of sodium valproate

   3. Any use of the following prohibited medications for the duration of the clinical
   study:

      1. Anticonvulsants

      2. Clonidine

      3. SSRIs and serotonin and norepinephrine re-uptake inhibitors (SNRIs)

      4. MAOIs

      5. TCAs

      6. Hypnotics

      7. Anxiolytics

      8. Sedating antihistamines

      9. Antipsychotics

   10. Other experimental medications designed to treat narcolepsy, cataplexy or any
      other condition

   4. Treatment with any investigational products within 3 months before study enrollment

   5. Any drug known to affect sleep-wake function. Concomitant stimulant use is permitted

   6. Additional exclusion criteria per protocol