Inclusion Criteria:

• Confirmed relapsing-remitting or secondary progressive multiple sclerosis.
• Ambulatory for distance of at least 100 meters without gait assistance.
• Persistent fatigue for at least 8 weeks that is not attributable to causes other than MS.
• Will be able to complete questionnaires and cognitive testing.

Exclusion Criteria:

• Other evident causes for fatigue:
  • Untreated depression or screening Center for Epidemiologic Studies Depression (CES-D) scale greater than 28;
  • Significant cognitive impairment (Baseline Short Test of Mental Status score of less than 29/38);
  • Narcolepsy, uncontrolled sleep apnea, or other primary sleep disorder judged to be likely a major contributor to fatigue;
  • Screening Epsworth Sleepiness Scale score greater than 15;
  • Uncontrolled hypothyroidism or anemia;
  • Other medical illness judged by the investigator to affect the participant''s fatigue complaints including current viral, bacterial, mycobacterial, or fungal infection.
• MS Disease Activity and Treatment:
  • Clinical exacerbations within 2 weeks prior to screening visit;
  • Corticosteroid use within 4 weeks prior to screening visit;
  • Beta-interferon, glatiramer acetate, immunosuppressant drugs (mitoxantrone, azathioprine, etc.) are permitted if a stable dose has been used for greater than or equal to 4 weeks and there is no temporal association of drug administration with perceived fatigue; elective on-study dose/regimen changes are not permitted.
• Current or Recent Fatigue Therapy and Other Medications:
  • Use of more than two doses of ASA (aspirin) greater than 81 mg/d within 2 weeks of screening visit;
  • Use of MS fatigue medications within 2 weeks of screening visit (including amantadine or Central Nervous System stimulants such as modafinil, methylphenidate, and pemoline);
  • Symptomatic medications (antidepressants, anti-spasticity agents, non-narcotic analgesics) are permitted if a stable dose has been used for > 4 weeks prior to screening for antidepressants and > 2 weeks prior to screening for other symptomatic therapies and there is no temporal association of drug administration with perceived fatigue; elective on-study dose changes are not permitted;
  • Current use of acetazolamide, antiplatelet agents or anticoagulants, COX-2 inhibitors, methotrexate, oral hypoglycemic medications.
• Medical Contraindications to ASA use:
  • Allergy to ASA or Non-Steroidal Anti-Inflammatory drugs;
  • Syndrome of asthma, rhinitis and nasal polyps;
  • History of confirmed peptic ulcer or gastrointestinal or severe gynecological bleeding.
• General Health Concerns:
  • Significant uncontrolled disease of cardiovascular, pulmonary, hepatic, renal, endocrine, rheumatological, neurological, gynecological, or gastrointestinal systems;
  • Pregnancy or unwillingness to utilize contraception;
  • History of alcohol or drug abuse within 6 months of screening or current alcohol intake > 3 drinks/day.
• Laboratory Exclusions (available values obtained within 8 weeks prior to screening visit are acceptable for all except the pregnancy test):
  • Positive pregnancy test;
  • Hemoglobin less than 11.0 g/dL (women) or 13.0 g/dL (men);
  • Platelet count < 120,000/μL;
  • Serum creatinine level > 1.4 mg/dL (women) or 1.6 mg/dL (men) ;
  • Aspartate aminotransferase (AST/SGOT) or alanine aminotransferase (ALT/SGPT) level greater than 2.5 times the upper limit of normal.