modafinil ('Provigil') is a memory-improving and mood-brightening psychostimulant. It enhances wakefulness and vigilance, but its pharmacological profile is notably different from the amphetamines, methylphenidate (Ritalin) or cocaine. Modafinil is less likely to cause jitteriness, anxiety, or excess locomotor activity - or lead to a hypersomnolent 'rebound effect' - than traditional stimulants. Subjectively, it feels smoother and cleaner than the amphetamines too.
Current research suggests modafinil, like its older and better-tested analogue adrafinil, is a safe, effective and well-tolerated agent. It is long-acting and doesn't tend to cause peripheral sympathetic stimulation. Yet its CNS action isn't fully understood. Modafinil induces wakefulness in part by its action in the anterior hypothalamus. Its dopamine-releasing action in the nucleus accumbens is weak and dose-dependent; the likelihood of dose-escalation and tolerance is apparently small. Modafinil has central alpha 1-adrenergic agonist effects i.e. it directly stimulates the receptors. More significant, perhaps, is its ability to increase excitatory glutamatergic transmission. This reduces local GABAergic transmission, thereby diminishing GABA(A) receptor signalling on the mesolimbic dopamine terminals.
Modafinil is proving clinically useful in the treatment of narcolepsy, a neurological disorder marked by uncontrollable attacks of daytime sleepiness. Narcolepsy is caused by dysfunction of a family of wakefulness-promoting and sleep-suppressing peptides, the orexins. Orexin neurons are activated by modafinil. Orexinergic neurons are found exclusively in the lateral hypothalamic area, but their fibers project to the entire central nervous system. Genetically modified orexin-knockout animals offer a model of human narcolepsy.
Experimentally, modafinil is also used in the treatment of Alzheimer's disease, depression, attention-deficit disorder, myotonic dystrophy, age-related memory decline, idiopathic hypersomnia and everyday cat-napping.
Prudence, however, should be exercised in drastically curtailing one's sleep. Prolonged sleeplessness weakens immune function. Animals tortured in sleep-deprivation experiments eventually die from massive bacterial infections of the blood..."