A Multicenter Study of the Efficacy and Safety of Xyrem With an Open- Label Pharmacokinetic Evaluation and Safety Extension in Pediatric Subjects With Narcolepsy With Cataplexy

Inclusion Criteria: 1. Male or female subjects aged 7-16 years at Visit 2 for subjects on Xyrem at study entry and at Visit 1.1 for Xyrem-naïve subjects (to ensure subjects are \<18 years of age at the end of the study) 2. Have a primary diagnosis of narcolepsy with cataplexy that meets International Classification of Sleep Disorders (ICSD)-2 or ICSD-3 criteria, whichever was in effect at the time of the diagnosis or, with the permission of the Medical Monitor, completes a Multiple Sleep Latency Test (MSLT) during Screening to confirm the diagnosis of Type 1 narcolepsy by ICSD-3 criteria (i.e., the subject meets all other ICSD-3 criteria for Type 1 narcolepsy) 3. Have given documented assent indicating that he/she was aware of the investigational nature of the study and the required procedures and restrictions before participation in any protocol-related activities 4. Have parent(s)/guardian(s) who have given informed consent for his/her/their child's participation in the study 5. Be willing to spend the required number of nights (2 to 3) in a sleep laboratory for PSG evaluations 6. If currently treated with Xyrem, must have been taking unchanged doses (twice nightly dosing no higher than 9 g/night) of Xyrem, and stimulants, if applicable, for the treatment of narcolepsy symptoms for at least 2 months prior to screening In addition to the above inclusion criteria, subjects participating in the PK evaluation must meet the following inclusion criteria: 7\. Be willing to spend 2 additional nights in the clinic for PK evaluation \- Exclusion Criteria: 1. Inability to understand assent or follow study instructions for any reason, in the opinion of the Investigator 2. Parent(s) or guardian(s) unable to comply with the requirements of the study for any reason, in the opinion of the Investigator 3. Other documented clinically significant condition (including an unstable medical condition, chronic disease other than narcolepsy with cataplexy, or history or presence of another neurological disorder) that might affect the subject's safety and/or interfere with the conduct of the study in the opinion of the Investigator 4. Treatment with benzodiazepines, non-benzodiazepine anxiolytics/ hypnotics/sedatives, neuroleptics, opioids, barbiturates, diclofenac, valproate, phenytoin, ethosuximide within 2 weeks prior to enrollment (discontinuation for the purpose of study enrollment is permitted only if considered safe by the Investigator and approved by the Medical Monitor) 5. Treatment with any other medications that have anticataplectic effect (e.g., serotonin-norepinephrine reuptake inhibitors \[SNRIs\], selective serotonin reuptake inhibitors \[SSRIs\], or tricyclic antidepressants \[TCAs\]) within 1 month before Screening 6. Unsafe for the subject to receive placebo treatment for 2 weeks, in the opinion of the Investigator In addition to the above exclusion criteria, subjects participating in the PK evaluation must not demonstrate the following: \-