Modafinil vs Adrafinil: Prodrug, Prescription Drug and the Liver Question

One reaction separates the two. Adrafinil is a prodrug: the liver converts it into modafinil, which does most of the work.⁹ Modafinil is an approved, Schedule IV prescription medicine for specific sleep disorders in the US. Adrafinil has never been approved in the US, and France, the only country that sold it, took it off the market in 2011 after an unfavourable benefit-risk review.¹²⁶

Because adrafinil ends up as modafinil, many online guides present it as a legal shortcut to the same effect. That framing skips several things: the extra metabolic load, the liver enzyme monitoring its own French label advised, the thin human evidence and the legal grey zone it sits in.⁷

This page compares the two on chemistry, evidence, safety, drug testing and law. It does not give sourcing or dosing advice. If you are considering either for sleepiness or concentration problems, the useful first step is a clinician who can look for the cause.

At a glance

Property	Modafinil	Adrafinil
What it is	Wakefulness-promoting drug (eugeroic)	Prodrug converted to modafinil in the liver
Brand examples	Provigil (US), Alertec (Canada)	Olmifon (France only, 1985 to 2011)
Approved uses	US: narcolepsy, OSA, shift work disorder. UK/EU: narcolepsy only	None today; French approval ended 2011
US legal status	Schedule IV controlled substance, prescription only	Unapproved; FDA says not a dietary supplement
UK status	Prescription-only medicine (POM)	No UK licence
Canada status	Prescription drug (Alertec and generics)	No authorised drug product
Liver enzymes	GGT and alkaline phosphatase rises seen in trials	French label advised monitoring alkaline phosphatase
Human evidence	Many controlled trials; small effect in healthy adults	Very limited; mostly older French data and dog studies
Sport drug testing	WADA-prohibited in competition	WADA-prohibited; detected as adrafinil and modafinil

What each drug is and how adrafinil becomes modafinil

Modafinil is a wakefulness-promoting agent. Its US label notes that it binds to the dopamine reuptake site and increases extracellular dopamine, and that its effective elimination half-life after repeated doses is about 15 hours.¹

Adrafinil came first: it was discovered in the late 1970s by the French firm Lafon Laboratories. Chemically it is modafinil with an extra hydroxyl group on the amide nitrogen, and after swallowing it the body metabolises it mainly to modafinil, the active form.⁹ A 2020 forensic study found both adrafinil and modafinil in a volunteer’s hair after a single 200 mg dose.⁹

Why the prodrug step matters

Relying on the liver to make the active drug has three practical consequences. The effect depends on individual metabolism, so the amount of modafinil produced is less predictable. Users commonly report a slower onset than with modafinil itself. And the parent compound and other metabolites circulate too, adding exposure without adding benefit.

How modafinil acts

Modafinil is not an amphetamine, but it is not pharmacologically inert either. The US label describes psychoactive and euphoric effects, and changes in mood, perception and thinking, typical of other central nervous system stimulants.¹ Its long half-life is one reason people who take it later in the day report trouble sleeping.

Effects in practice: what studies and users describe

Modafinil’s approved purpose is narrow: improving wakefulness in adults with excessive sleepiness from narcolepsy, obstructive sleep apnoea or shift work disorder in the US.¹ Its off-label use as a study or work aid is widespread, but that is not what it was tested for.

For healthy, rested adults the evidence is modest. A 2019 meta-analysis of 19 placebo-controlled trials of a single dose found a small overall benefit across attention, executive function, memory and processing speed (Hedges’ g 0.10), and concluded there was only limited potential for modafinil as a cognitive enhancer outside sleep deprivation.¹⁰ No significant difference was seen between 100 mg and 200 mg doses in that analysis.

Even within approved uses the picture is not uniform. When the EMA reviewed modafinil in 2010, it concluded that for sleep apnoea, shift work disorder and idiopathic hypersomnia, the risks of skin, hypersensitivity and neuropsychiatric reactions outweighed the evidence for clinically important benefit.³ The US label still includes sleep apnoea and shift work disorder, a reminder that regulators can read the same data differently.

Adrafinil’s human evidence is thinner still. Its French approval covered attention and alertness problems with psychomotor slowing in elderly people. When the French regulator re-examined the data in 2011, it concluded that the clinical studies did not allow any conclusion about benefit in that group.⁶ Much of the widely cited research is in aged dogs, where adrafinil increased activity and improved learning on one discrimination task.¹²

Users of both describe greater alertness and reduced sleepiness, and some report headaches, anxiety or poor sleep if taken late in the day. Those reports are uncontrolled, and people who seek out adrafinil online are not a representative group.

Evidence quality compared

• Modafinil: regulatory-grade randomised trials in sleep disorders, plus many small studies in healthy volunteers. The healthy-volunteer effects are small and task-dependent.¹⁰
• Adrafinil: no modern randomised trials in people that we could find; a French regulator judged the sponsor’s data insufficient; animal studies fill much of the gap.⁶¹²

The argument that adrafinil is “basically modafinil” rests on the metabolic conversion, not on head-to-head human trials. No published trial has compared the two directly for effect or safety in people.

Safety: liver enzymes, skin reactions and interactions

The liver question

Adrafinil’s reputation for being hard on the liver traces to its own label. The French summary of product characteristics advised monitoring alkaline phosphatase during prolonged treatment.⁷ That is an enzyme-monitoring precaution, not documented evidence of widespread liver injury, but it means the manufacturer considered liver effects worth checking.

Modafinil is not free of this issue. In US placebo-controlled trials, mean GGT and alkaline phosphatase were higher with modafinil than placebo, though not to clinically abnormal levels, and the dose is halved in severe hepatic impairment.¹ Anyone with liver disease, or who drinks heavily, has a reason to avoid unsupervised use of either.

Other risks

• Serious skin reactions: modafinil’s US label carries a warning about serious rash, including a possible case of Stevens-Johnson syndrome in paediatric trials; the EU restricted its use in 2010 partly for this reason and advised against prescribing to children.¹³
• Psychiatric and cardiovascular effects: the EU review cited neuropsychiatric disorders and cardiovascular risks, adding contraindications in uncontrolled hypertension and arrhythmias.³
• Contraception: modafinil can reduce the effectiveness of hormonal contraceptives during use and for one month after stopping.¹ Because adrafinil becomes modafinil, the same caution is reasonable, though it has not been formally studied.
• Dependence: modafinil is controlled because of its abuse potential, and UK prescribing information notes that dependence with long-term use cannot be excluded.¹⁴
• Adrafinil label effects: agitation, insomnia, headache, stomach pain, skin eruptions and, rarely, involuntary facial movements.⁷

Legal status in September 2026

United States: modafinil is a Schedule IV controlled substance under 21 CFR 1308.14, available only on prescription.² Adrafinil is not approved by the FDA and is not listed in the federal controlled substance schedules. In a 2019 warning letter the FDA stated that adrafinil, along with piracetam, noopept and several racetams, is not a dietary supplement, so selling it with health claims makes it an unapproved new drug.⁸ State rules can differ.

United Kingdom: modafinil is a prescription-only medicine, licensed only for excessive sleepiness in narcolepsy.⁴ Adrafinil has no UK licence; selling it for human consumption risks falling under medicines law or the Psychoactive Substances Act 2016.

European Union: since 2010, modafinil has been limited to narcolepsy after the EMA concluded that risks outweighed benefits for other sleep disorders.³

France: Olmifon (adrafinil) had been sold only in France since 1985. Its maker stopped supplying it in August and September 2011, and in December 2011 the regulator’s licensing committee judged its benefit-risk balance unfavourable and proposed withdrawing the authorisation.⁶

Canada: modafinil is a prescription drug, marketed as Alertec since 1999; we found no adrafinil product listed in Health Canada’s Drug Product Database.⁵

Drug tests, sport and look-alike products

Standard workplace drug panels are not designed to find either compound, but targeted tests can. The World Anti-Doping Agency added both to its prohibited list in 2004, and both remain banned in competition; forensic methods can detect adrafinil and modafinil together after one dose.⁹¹¹ Because adrafinil turns into modafinil, taking it offers no protection against a positive sport test.

A newer problem is analogues. The 2026 WADA Prohibited List added flmodafinil and fladrafinil, halogenated relatives of the two drugs that USADA says have turned up in dietary supplements and “research only” products.¹¹ Our explainer on what research use only really means covers why that label offers consumers no safety assurance.

Red flags on any wakefulness product

• Any product sold without a prescription that contains modafinil, armodafinil or a named analogue.
• Vague ingredient names such as “eugeroic complex” or “wakefulness matrix”.
• “Not for human consumption” wording on something clearly designed to be swallowed.
• No batch-specific lab report. Even a genuine certificate of analysis says nothing about safety or legality.
• Websites offering prescription modafinil without a prescription. In the US and UK that supply is unlawful, and the buyer has no way to verify what the tablets contain.

If the goal is alertness, compare the evidence for better-studied options such as caffeine, and read about nootropic tolerance before relying on any stimulant daily.

Frequently asked questions

Is adrafinil the same as modafinil?

No, but they are closely related. Adrafinil is a prodrug that the liver converts mainly into modafinil, so much of its effect comes from modafinil. The difference is the extra metabolic step, a less predictable amount of active drug, and the fact that adrafinil lacks the regulatory approval and trial base that modafinil has.⁹

Is adrafinil legal in the US?

Adrafinil is not a federally controlled substance, but it is not an approved drug either. The FDA has stated that adrafinil is not a dietary supplement, so marketing it for health effects makes it an unapproved new drug. It occupies a grey area rather than being clearly lawful to sell for human use.⁸

Is adrafinil bad for your liver?

The concern is real but often overstated online. Adrafinil’s French label advised monitoring alkaline phosphatase during prolonged use, which signals liver enzyme effects rather than proven liver damage. Modafinil also raised GGT and alkaline phosphatase slightly in US trials. People with liver disease should avoid unsupervised use of either.⁷¹

Why was adrafinil discontinued?

In 2011 France reviewed adrafinil, then sold as Olmifon for alertness problems in older people. The regulator’s committee found the clinical data did not show benefit and, given known side effects, judged the benefit-risk balance unfavourable. The manufacturer had already stopped supplying it in August and September 2011.⁶

Does adrafinil show up on a drug test?

Routine workplace drug panels do not normally look for it. Targeted tests, including sport anti-doping tests, can detect both adrafinil and its metabolite modafinil. Both are prohibited in competition by WADA, so an athlete using adrafinil would test positive for a banned stimulant.⁹¹¹

Sources

1. Cephalon, Inc. PROVIGIL (modafinil) tablets, prescribing information. Revised January 2015. US Food and Drug Administration. accessdata.fda.gov
2. Code of Federal Regulations. 21 CFR 1308.14, Schedule IV, paragraph (f) Stimulants: Modafinil (1680). ecfr.gov
3. European Medicines Agency. European Medicines Agency recommends restricting the use of modafinil. Press release, 22 July 2010. ema.europa.eu
4. Milpharm Ltd. Modafinil 100 mg tablets: summary of product characteristics. Legal category POM. Revised 14 February 2024. Electronic Medicines Compendium. medicines.org.uk
5. Health Canada. Drug Product Database: ALERTEC (modafinil), DIN 02239665, schedule: Prescription. health-products.canada.ca
6. Afssaps. Point d’information sur les dossiers discutés en commission d’AMM, séance du jeudi 1er décembre 2011 (Réévaluation du rapport bénéfice/risque des médicaments à base d’adrafinil). Communiqué, 2 December 2011. Archived copy: web.archive.org (ansm.sante.fr)
7. ANSM. OLMIFON 300 mg, comprimé pelliculé (adrafinil): résumé des caractéristiques du produit. agence-prd.ansm.sante.fr
8. US Food and Drug Administration. Warning letter to Peak Nootropics LLC aka Advanced Nootropics, MARCS-CMS 557887. 4 February 2019. fda.gov
9. Ameline A, Gheddar L, Raul JS, Kintz P. Identification of adrafinil and its main metabolite modafinil in human hair. Self-administration study and interpretation of an authentic case. Forensic Sci Res. 2020;5(4):322-326. DOI: 10.1080/20961790.2019.1704482. PMID: 33457050. pubmed.ncbi.nlm.nih.gov
10. Kredlow MA, Keshishian A, Oppenheimer S, Otto MW. The efficacy of modafinil as a cognitive enhancer: a systematic review and meta-analysis. J Clin Psychopharmacol. 2019;39(5):455-461. DOI: 10.1097/JCP.0000000000001085. PMID: 31433334. pubmed.ncbi.nlm.nih.gov
11. US Anti-Doping Agency. Athlete advisory: what’s new on the 2026 WADA Prohibited List? Published 16 October 2025. usada.org
12. Siwak CT, Callahan H, Milgram NW. Adrafinil: effects on behavior and cognition in aged canines. Prog Neuropsychopharmacol Biol Psychiatry. 2000;24(5):709-726. DOI: 10.1016/s0278-5846(00)00103-2. PMID: 11191710. pubmed.ncbi.nlm.nih.gov

Editorial note: This article is for general information only and is not medical or legal advice. Modafinil is a prescription medicine; use it only as prescribed and supervised by a licensed clinician. Adrafinil is not approved by the FDA for any use. Laws vary by location and change often, so verify the rules that apply where you are. Always talk to a licensed healthcare provider before use, especially if you are under 21, pregnant or nursing, taking medication, or managing a health condition.