To date, my patients have used modafinil between 5 and 13 months, and there has been no evidence of tolerance or decreased effectiveness and no apparent adverse interactions with concurrent medications. Side effects, when present, have usually been mild and transient, primarily complaints of stimulation or gastrointestinal upset. It should be noted, however, that outside of this group, two middle-aged brain-injured women with multiple other complications and medications could not tolerate modafinil. This was due to strong feelings of emotional instability brought on soon after taking the first dose of 100 mg. Both reported similar reactions to many other medications and felt they were generally hypersensitive to drugs. No further trials were made at a lower dose.