In a series of 21 PBC patients with excessive daytime sleepiness [313] , the centrally acting agent modafinil was investigated in an open-label study [314] . Significant improvement was seen in Epworth Sleepiness Scale scores and fatigue severity as assessed by PBC-40 fatigue domain score, but the drug had to be stopped due to side effects in a considerable part of the patients before the end of the study.