In the United States, modafinil is approved by the U.S. Food and Drug Administration only for the treatment of narcolepsy, shift work sleep disorder, and as an adjunct treatment for obstructive sleep apnea/hypopnea.^[36] In some countries, it is also approved for other hypersomnias, like idiopathic hypersomnia. The usual prescribed dosage for these disorders is 200 mg once a day (less commonly, 100 to 400 mg/day in one or two doses).

For conditions other than shift work sleep disorder, modafinil is normally taken in one dose in the morning or in two doses in the morning and at midday. It is generally not recommended to take modafinil after noon: modafinil is a relatively long-acting drug with a half-life of 15 hours, and taking it during the later part of the day carries a risk of sleep disturbances.^{[37][unreliable medical source?]}

Because of the risk for development of skin or hypersensitivity reactions and neuropsychiatric disorders, the European Medicines Agency has recommended that new patient prescriptions should only be to treat sleepiness associated with narcolepsy.^[38] Because any serious side effects will usually appear within the first twelve weeks, the guidance does not require patients already receiving treatment to stop taking the drug.^[39]

ADHD[edit]

Modafinil was shown to be an effective treatment for attention deficit hyperactivity disorder(ADHD);^[40] however, in 2006, it was found by the FDA to be unfit for use by children for that purpose. It was rejected primarily due to two cases of serious skin rash, suspected to have been Erythema multiformeor Stevens–Johnson syndrome, among 933 subjects receiving the drug.^{[41][42][43][44]} Cephalon's own label for Provigil now discourages its use by children for any purpose.^[40]

Psychiatric/neurodegenerative disorders[edit]

Other potentially effective, but unapproved uses include the treatment of depression,^[45] bipolar depression,^[46][47] opiate^[48] and cocaine dependence,^[49] Parkinson's disease,^[50] schizophrenia,^[51] and disease-related fatigue,^[52][53] as well as fatigue that is the side effect of another medication.^[54]

Modafinil may be also an effective and well-tolerated treatment in patients with seasonal affective disorder.^[55]

A randomized double-blind study of modafinil showed that normal healthy volunteers between the ages of 30-44 showed general improvement in alertness as well as mood. In the three-day study, counterbalanced, randomized, crossover, inpatient trial of modafinil 400 mg was administered as well as a placebo to the control group. The conclusion demonstrated that modafinil may have general mood-elevating effects in particular for the adjunctive use in treatment-resistant depression.^[56]

Depersonalization disorder[edit]

Modafinil used alone has been reported to be effective in a subgroup of individuals with depersonalization disorder; the subgroup of people with depersonalization disorder most likely to respond are those who have attentional impairments, under-arousal and hypersomnia. However, clinical trials have not been conducted.^[57] Dr. Evan Torch calls a combination of an SSRI and Modafinil "the hidden pearl that can really help depersonalization disorder".^[58]

Cognitive enhancement[edit]

There is disagreement to whether the cognitive effects modafinil showed in healthy non-sleep-deprived people are sufficient to consider it to be acognitive enhancer.^[59][60][61] The researchers agree that modafinil improves some aspects of working memory, such as digit span, digit manipulation and pattern recognition memory, but the results related to spatial memory, executive function and attention are equivocal.^{[59][60][61][62]} Some of the positive effects of modafinil may be limited to "lower-performing"^[62] individuals.^[63] One study found that modafinil restored normal levels of learning ability in methamphetamine addicts, but had no effect on non-addicts.^[64]

There is evidence of neuroprotective effects in rats.^[65]

Multiple Sclerosis[edit]

Modafinil has also found off-label use with the neurological fatigue reported by some with multiple sclerosis.^[66] In 2000, Cephalon conducted a study to evaluate modafinil as a potential treatment for MS-related fatigue. A group of 72 people with MS of varying degrees of severity tested two different doses of modafinil and an inactive placebo over nine weeks. Fatigue levels were self-evaluated on standardized scales. Participants taking a lower dose of modafinil reported feeling less fatigued and there was a statistically significant difference in fatigue scores for the lower dose versus the placebo. The higher dose of modafinil was not reported to be significantly more effective.^[67][68]

Fatigue[edit]

Modafinil is also used off-label to treat sedation and fatigue in many conditions, including depression,^[69][70] fibromyalgia, chronic fatigue syndrome,myotonic dystrophy,^[71] opioid-induced sleepiness,^[72] spastic cerebral palsy,^[73] and Parkinson's disease.^[74] Modafinil has been shown to improve excessive daytime somnolence and fatigue in primary biliary cirrhosis.^[56]

It has been reported to reduce jet lag^[75] and increase subjective mood and friendliness among shift workers.^[76] It is also prescribed by sleep physicians for delayed sleep phase syndrome, which causes excessive daytime somnolence when the natural (delayed) diurnal rhythm is replaced by a socially determined earlier or forward shifted sleep schedule.^[77] The resultant wakefulness and neuro-behavioural impairments are comparable to those of travel-associated jet lag and persist as long as the forward shifted sleep schedule is maintained. A similar phenomenon commonly experienced by students and workers with varying sleep schedules during the week is often referred to as "social jet lag" and has been implicated in metabolic disorders and obesity.^[78]

Cocaine addiction[edit]

Modafinil is under investigation as a possible method to treat cocaine dependence, for several reasons involving biochemical mechanisms of the two drugs, as well as the observation that clinical effects of modafinil are largely opposite to symptoms of cocaine withdrawal.

The pilot 8-week double-blind study of modafinil for cocaine dependence (2004) produced inconclusive results. The number of cocaine-positive urine samples was significantly lower in the modafinil group as compared to the placebo group in the middle of the trial, but by the end of the 8 weeks the difference stopped being significant. Even before the treatment began, the modafinil group had lower cocaine consumption further confounding the results. As compared to placebo, modafinil did not reduce cocaine craving or self-reported cocaine use, and the physicians ratings were only insignificantly better.^[79] Dan Umanoff, of the National Association for the Advancement and Advocacy of Addicts, criticized the authors of the study for leaving the negative results out of the discussion part and the abstract of the article.^[80][81]

A later double-blind study of modafinil in people seeking treatment for cocaine dependence found no statistically significant effect on the rate of change in percentage of cocaine non-use days, but noted a significant improvement in some secondary outcomes such as the maximum number of consecutive non-use days for cocaine.^[82]

Post-chemotherapy cognitive impairment[edit]

Modafinil has been used off-label in trials with people with symptoms of post-chemotherapy cognitive impairment, also known as "chemobrain", but in 2011 it was found to be no better than placebo.^[83] As of 2011 there was no evidence to support using it to reduce fatigue in palliative care.^[84]

Weight loss[edit]

Studies on modafinil (even those on healthy weight individuals) indicate that it has an appetite reducing/weight loss effect.^{[76][85][86][87][88]} All studies on modafinil in the Medline database that are for one month or longer which report weight changes find that modafinil users experience weight loss compared to placebo.^[89] In 2008, one small-scale study on individuals performing simulated shift work quantified the effect as a 18% decrease in total caloric intake on 200 mg/day, and a 38% decrease on 400 mg/day.^[90]

However, the prescribing information for Provigil notes that "There were no clinically significant differences in body weight change in patients treated with PROVIGIL compared to placebo-treated patients in the placebo-controlled clinical trials."^[91]

In experimental studies, the appetite reducing effect of modafinil appears to be similar to that of amphetamines, but, unlike amphetamines, the dose of modafinil that is effective at decreasing food intake does not significantly increase heart rate. Also, an article published in the Annals of Clinical Psychiatry, presented the case of a 280 pound patient (BMI=35.52) who lost 40 pounds over the course of a year on Modafinil (to 30.44 BMI). After three years, his weight stabilized at a 50 pound weight loss (29.59 BMI). The authors conclude that placebo controlled studies should be conducted on using Modafinil as a weight loss agent.^[85] Conversely, a US patent (#6,455,588) on using modafinil as an appetite stimulating agent has been filed by Cephalon in 2000.