Safety and Efficacy of Xyrem Oral Solution (Sodium Oxybate) Compared With Placebo in Narcoleptic Patients

INCLUSION CRITERIA * Have signed \& dated informed consent before beginning protocol procedures. * Willing \& able to complete entire trial as described in protocol. * 16 years of age or older. * Have a history and presenting symptoms of excessive daytime sleepiness. * Have a history of cataplexy localizable to a specific muscle group(s) or part(s) of body during which the patient is lucid (not experiencing an inadvertent nap or micro sleep). * Have valid PSG \& MSLT scores (collected during an overnight test) within last five years and a current diagnosis of narcolepsy according to the following criteria established by the American Sleep Disorders Association: (1) Recurrent daytime naps or lapses into sleep occur almost daily for at least 3 months; (2) Sudden bilateral loss of postural muscle tone occurs in association with intense emotion (cataplexy); (3) Polysomnography demonstrates one or more of the following: (a) Sleep latency less than 10 minutes; (b) REM sleep latency less than 20 minutes; (c) An MSLT that demonstrates a mean sleep latency of less than 5 minutes; (d) Two or more sleep-onset REM periods * Females who are surgically sterile, two years post-menopausal, or if of child-bearing potential, using a medically accepted method of birth control and agree to continue use of this method for the duration of the trial. * In the opinion of the investigator, have adequate support for the duration of trial to include transportation to and from trial site. In addition, if in the investigator's assessment it is clinically indicated, the patient is willing to not operate a car or heavy machinery for the duration of the trial or for as long as the investigator deems clinically indicated. EXCLUSION CRITERIA * Received gamma-hydroxybutyrate in the last 30 days. * Have taken any investigational therapy within 30-day period prior to initial screening visit for this trial. * Patients taking fluoxetine (Prozac). * Have been diagnosed with sleep apnea syndrome, defined as an Apnea Index \> 10 per hour or an Apnea Hypopnea Index greater than 15 per hour, or have any other cause of daytime sleepiness, and have any other disorder(s) that can be considered a primary cause of excessive daytime sleepiness. * Taking hypnotics, tranquilizers, antihistamines (except for non-sedating antihistamines), benzodiazepines or clonidine at the start of the baseline period. Patients taking anticonvulsants are not eligible to participate even if willing to washout anticonvulsants for the trial. * Experiencing unstable cardiovascular, endocrine, neoplastic (excluding localized basal cell carcinoma), gastrointestinal, hematologic, hepatic, immunologic, metabolic, neurological (other than narcolepsy/cataplexy), pulmonary, and/or renal disease which would place the patient at risk during the trial or compromise objectives outlined in the protocol. * Have psychiatric disorders, major affective or psychotic disorders, or other problems that, in the investigator's opinion, would preclude the patient's participation and completion of this trial or compromise reliable representation of subjective symptoms. * Have current or recent (within one year) history of a substance use disorder including alcohol abuse as defined by DSM-IV. * Serum creatinine greater than 2.0 mg/dL, abnormal liver function tests (SGOT \[AST\] or SGPT \[ALT\] more than twice the upper limit of normal), or elevated serum bilirubin (more than 1.5 times upper limit of normal), or pre-trial ECG results demonstrating clinically significant arrhythmias, greater than a first degree AV block or a history of myocardial infarction within last six months. * Have an occupation that requires variable shift work or routine night shift. * Have a clinically significant history of seizure disorder, a history of clinically significant head trauma (i.e., concussion resulting in clinically significant loss of consciousness) or past invasive intracranial surgery, and are taking anticonvulsant medications.