Patients will be followed up for max 18 months. Information on the Adverse Events and potential misuse or abuse of Xyrem ® will be collected.

Observational Study to Evaluate Risks of Side Effects, Drug Abuse and Dependence in Patients Who Received Xyrem ® on Prescription

Post Marketing Non-interventional Surveillance Pharmacoepidemiology Study (PMSS) to Evaluate Long-term Safety, Tolerability and Compliance in Administration of Xyrem® (Sodium Oxybate) Oral Solution in Patients Who Receive Treatment With This Medication in Regular Clinical Practice.