- The patient has excessive sleepiness associated with a diagnosis of narcolepsy or Obstructive Sleep Apnea/Hypopnea Syndrome (OSAHS) according to the International Classification of Sleep Disorders (ICSD) criteria. For OSAHS, the patient must be a regular nasal continuous positive airway pressure (nCPAP) therapy user (usage at least 4 hours/night on at least 70% of nights), must have documented adequate education and intervention efforts to encourage nCPAP therapy use, the patient's nCPAP therapy regimen must be stable for at least 4 weeks prior to study entry, and the patient's nCPAP therapy must be effective in the opinion of the investigator.