Inclusion Criteria:

Patients are included in the study if all of the following criteria are met:

• Men and women (outpatients) of any ethnic origin, between 18 and 65 years of age (inclusive) at the beginning of the respective double-blind study, are eligible.
• The patient has completed a cephalon-sponsored double-blind study (study C10953/3020/NA/MN, C10953/3021/AP/MN, C10953/3022/CM/MN, or C10953/3025/AP/MN), and the investigator has recommended they be enrolled.
• Patients with OSAHS must continue to be regular users of nCPAP therapy, which the investigator considers to remain effective. Patients with chronic SWSD must work 5 nights/month, with night shifts including at least 6 hours between 2200 and 0800 that are no longer than 12 hours in duration.
• The patient is considered to be in good health.
• Women must be surgically sterile, 2 years postmenopausal, or if of childbearing potential, must use a medically accepted method of birth control (ie, barried method with spermacide, steroidal contraceptive [oral, implanted, and Depo-Provera contraceptives must be used in conjunction with a barrier method], or intrauterine device [IUD]).
• The patient must be willing and able to comply with study restrictions and to attend regularly scheduled clinic visits as specified in this protocol.

Exclusion Criteria:

Patients are excluded from participating in this study if 1 or more of the following criteria are met:

• Have any clinically significant, uncontrolled medical conditions (treated or untreated).
• Have a probable diagnosis of a current sleep disorder other than the primary diagnosis of narcolepsy, OSAHS, or chronic SWSD.
• Consume caffeine including coffee, tea and/or other caffeine-containing beverages or food averaging more than 600 mg of caffeine.
• Use any prescription drugs disallowed by the protocol (as identifed in section 5.2) or clinically significant use of over-the-counter (OTC) drugs within 7 days before visit 1.
• Have a history of alcohol, narcotic, or any other drug abuse as defined by the Diagnostic and Statistical Manual of the American Psychiatric Association, 4th Edition (DSM-IV) (American Psychiatric Association 1994).
• Have a positive urine drug screen (UDS) (subjects enrolling in this open-label study within 7 days after completing the double-blind study may be enrolled without UDS results).
• Have a clinically significant deviation from normal in the physical examination.
• Are pregnant or lactating. Any woman becoming pregnant during the study will be withdrawn from the study.
• Have any disorder that may interfere with drug absorption, distribution, metabolism, or excretion (including gastrointestinal surgery).
• Have a known clinically significant drug sensitivity to stimulants.