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Fatigue, defined as a subjective lack of physical or mental energy to carry out usual and desired activities as perceived by the patient or caregiver, 1 is common and one of the most disabling symptoms of multiple sclerosis (MS). Fatigue affects 75%-90% of patients with MS, 2- 5 with as many as 46%-66% experiencing fatigue on a daily basis. 4, 6 Unfortunately, despite its high prevalence, chronic nature, and association with disability, there is currently no accepted treatment for MS related fatigue. Various pharmacological agents have been used for its treatment, including amantadine, pemoline, aminopyridines, and selective serotonin reuptake inhibitors (SSRIs). Four short term studies indicated that fatigue was reduced with amantadine treatment in 20%-40% of patients with MS who had mild to moderate disability. 5, 7- 9 Studies have suggested that high dosages of pemoline (75 mg/day) are needed to achieve any improvement in MS related fatigue, 7, 10 but even with a high dosage the improvement was not significant when compared with placebo treatment. Although sometimes used in the treatment of MS related fatigue, no controlled clinical studies of the efficacy and safety of aminopyridines or SSRIs have been published. Therefore, the use of these agents for the treatment of MS related fatigue is not recommended. 1
Modafinil, a novel wake promoting agent, is effective and well tolerated for the treatment of excessive daytime sleepiness (EDS) in patients with narcolepsy. 11- 13 After 9 weeks of double blind treatment with 200 mg/day and 400 mg/day modafinil in two pivotal double blind studies of modafinil for the treatment of EDS in patients with narcolepsy, the mean SF-36 vitality scores significantly improved by 11 points and 13 points over the baseline scores. 14 The improvements in vitality found after treatment with modafinil were significant (p<0.05 compared with placebo) and were maintained during 40 weeks of subsequent open label treatment with modafinil. 14 In a 6 week open label trial of 151 patients with narcolepsy who had been unsatisfactorily treated for EDS with CNS stimulants, treatment with modafinil significantly improved wakefulness and also significantly improved fatigue as assessed using both the SF-36 and the profile of mood states (POMS) questionnaire. 15 Therefore, it was of interest to investigate the effect of modafinil on the fatigue...