Modafinil

This page is a reference summary of published evidence and regulatory documents. It is not a substitute for individual medical advice, and it is not a recommendation to take or avoid any medicine.

Medically reviewed by Dr. Sofia Lindqvist, · Last reviewed 11 August 2026

Modafinil is a prescription wakefulness-promoting agent. Its class name is eugeroic, from the Greek for “good arousal.” It was developed in France in the 1970s, approved by the FDA in 1998 as Provigil, and has been available generically in the United States since 2012.

It was designed to do one thing: restore wakefulness in people whose wakefulness is pathologically impaired. Everything else it is used for sits outside that original intent.

At a glance

200 mg

standard daily dose

~15 h

elimination half-life

2–4 h

time to peak concentration

C-IV

US control status

Two numbers carry most of the practical weight: the dose, which barely changes across indications, and the half-life, which is long enough that the time you take it determines how you sleep that night.

Approved uses

Condition	What modafinil does	What it does not do
Narcolepsy	Reduces excessive daytime sleepiness and sleep attacks	Does not modify the underlying neurological disorder, and does not treat cataplexy
Obstructive sleep apnea	Treats sleepiness that persists despite adequate treatment of the airway obstruction	Does not treat the apnea; CPAP or another primary therapy must continue
Shift work disorder	Reduces sleepiness during scheduled waking hours on night or rotating shifts	Does not realign circadian timing

In sleep apnea, modafinil is an adjunct. The label is explicit that it does not address the obstruction, the oxygen desaturation, or the cardiovascular risk that comes with them.

Off-label and unapproved use

Physicians prescribe modafinil off-label for fatigue in multiple sclerosis, ADHD, depression-related fatigue, chronic fatigue syndrome and cancer-related fatigue. Off-label prescribing is legal and routine; the evidence behind it varies a great deal from one indication to the next.

Separately, modafinil is widely used without a prescription as a cognitive enhancer — by students, shift workers, military personnel and knowledge workers. That use is not approved anywhere, and obtaining the drug without a prescription is illegal in the US and most other countries. The research on cognitive effects, covered in the evidence section, was generated under controlled conditions with monitored dosing, which is not what unsupervised use looks like.

How it works

Modafinil’s mechanism is unusual and still incompletely characterised. It was found to be clinically useful well before anyone identified what it binds to.

The clearest finding is that it binds the dopamine transporter, inhibiting reuptake and raising extracellular dopamine in the striatum and nucleus accumbens. PET imaging in living brains has confirmed that occupancy. Beyond that it raises norepinephrine and glutamate, lowers GABA, and activates the orexin and histamine systems of the hypothalamus.

DAT binding

weak, distinct conformation

Dopamine ↑

striatum, accumbens

Orexin + histamine ↑

hypothalamus

Sustained wakefulness

The chain from transporter binding to wakefulness. The downstream hypothalamic effects are as important to the clinical picture as the dopamine step.

Three features are thought to explain its comparatively low abuse liability: the binding affinity is weak relative to classical stimulants, it occupies the transporter in a different conformation from cocaine-like inhibitors, and its onset is slow.

Pharmacokinetics

Modafinil is absorbed rapidly, peaking at roughly two to four hours. Food delays absorption by about an hour without changing the total amount absorbed. It is metabolised in the liver to inactive metabolites.

peak zero

23:00 bedtime

0h 4h 8h 12h 16h 20h 24h

Modafinil 200 mg at 07:00

Modelled plasma concentration after a single 200 mg morning dose. The curve is illustrative; individual clearance varies.

The elimination half-life is approximately fifteen hours. This is the single most practically important number about the drug: a dose taken at midday is still meaningfully active at bedtime.

Dosing

The label specifies 200 mg once daily for all three approved indications: in the morning for narcolepsy and sleep apnea, and about an hour before the shift for shift work disorder. Doses up to 400 mg have been studied without demonstrating additional benefit.

Safety

Modafinil is generally well tolerated. Headache is the most common adverse effect by a wide margin, followed by nausea, anxiety, insomnia and reduced appetite.

It also carries a rare risk of serious skin reactions, including Stevens–Johnson syndrome, toxic epidermal necrolysis and DRESS. These are uncommon and can be fatal. The guidance is to stop the drug at the first sign of a rash rather than watch it.

Pregnancy

Regulators in the European Union, United Kingdom, Canada and Australia have contraindicated modafinil in pregnancy since 2019, on the basis of suspected congenital malformations. The US position has differed. Modafinil also reduces the effectiveness of hormonal contraceptives, and those two facts compound.

Interactions

Modafinil is a moderate inducer of CYP3A4 and a weak inhibitor of CYP2C19. Clinically significant interactions include hormonal contraceptives, cyclosporine, warfarin, phenytoin and certain antidepressants.

Legal status and names

Modafinil is a Schedule IV controlled substance in the United States. Status varies internationally; some countries treat it as prescription-only without controlled scheduling.

It is sold under many names depending on the market, including Modalert and Modvigil. These are the same molecule from different manufacturers.

A prescription is required because the safety profile demands screening only a clinician can do: cardiac history, psychiatric history, liver function, pregnancy status and a full medication list.

Frequently asked questions

What is modafinil approved for?

In the US, modafinil (Provigil) is FDA-approved to reduce excessive sleepiness in narcolepsy, obstructive sleep apnea, and shift work disorder. It is not approved as a general cognitive enhancer.

Does modafinil treat sleep apnea?

No. In obstructive sleep apnea it treats the sleepiness that persists despite adequate treatment of the airway obstruction, usually with CPAP. The apnea itself is untouched, and primary therapy must continue.

Is modafinil the same as Provigil?

Yes. Provigil was the original brand, marketed by Cephalon and later Teva. Generic modafinil has been available in the US since 2012.

How long does modafinil last?

The elimination half-life is roughly fifteen hours. A dose taken at midday is still meaningfully active at bedtime, which is why timing matters more with modafinil than with shorter-acting stimulants.

Can modafinil be prescribed off-label?

Yes. Off-label prescribing is legal and routine, and modafinil is used for multiple sclerosis fatigue, ADHD, depression-related fatigue and cancer-related fatigue. The strength of the evidence varies considerably by indication.