[An experience of administration of modafinil for excessive daytime sleepiness in a patient with myotonic dystorophy].

We report the beneficial and adverse effects of modafinil for daytime sleepiness in a 62-year-old female patient with myotonic dystrophy. Although it was effective for excessive daytime sleepiness, orolingual dyskinesia appeared the day following administration of modafinil (100 mg/day), and dyskinesia disturbed her daily life including dental treatment. When modafinil was stopped, dyskinesia was improved. However, excessive daytime sleepiness deteriorated gradually; re-treatment with smaller dosage (50 mg every other day) resulted in partial improvement but aggravation of both dyskinesia and diabetes mellitus. Modafinil should be administered carefully when the patient is older or has complications such as glucose intolerance.