Armodafinil

The R-enantiomer of modafinil — the longer-acting half of the racemic mixture, sold as its own prescription drug for the same conditions: narcolepsy, shift-work disorder, sleep apnea. Users describe it as 'modafinil with a later peak', which is precisely what the pharmacokinetics show.

Armodafinil is the longer-lasting single isomer of modafinil — the same molecule, with the shorter-lived mirror-image half removed. FDA's label says the precise wakefulness mechanism is UNKNOWN; dopamine-transporter inhibition is the leading hypothesis, supported mainly by laboratory and animal work, with histamine, orexin and noradrenaline pathways proposed alongside. The practical difference from modafinil is not a later peak — both peak within a couple of hours fasted — but more sustained concentrations into the late day, which is why it is described as smoother and why it interferes with sleep further into the evening.

Same evidence base as modafinil: solid for wakefulness under sleep deprivation, modest for executive function in the well-rested. Head-to-head data against modafinil is limited; the practical difference is timing — later peak concentration, so alertness holds further into the day at the cost of a later sleep window.

• Approved to improve wakefulness in adults with excessive sleepiness associated with narcolepsy, shift-work disorder and obstructive sleep apnoea — the label is explicit that it does not treat the airway obstruction, which must still be treated on its own.
• The randomised evidence in those approved indications is solid.
• For cognitive enhancement in rested healthy adults: NONE SHOWN for armodafinil itself — the independent evidence is inadequate, and even modafinil's meta-analyses find only small, domain-specific effects. Borrowing modafinil's already-thin enhancement evidence is not a substitute.
• It carries the same serious label warnings: severe rash including Stevens-Johnson syndrome, multisystem hypersensitivity including DRESS and angioedema, and serious psychiatric reactions including mania, delusions, hallucinations and suicidal ideation.
• Like modafinil it is a scheduled drug with recognised abuse and dependence potential, lower than amphetamines but genuinely present.

Longer effective duration than modafinil at equivalent exposure, with concentrations sustained further into the day — which is the entire clinical rationale and also the main practical drawback, since an early dose can still be disrupting sleep at night. It induces CYP3A4, the liver enzyme that clears a large share of prescription drugs, which is the source of its most consequential interaction.

Same profile as modafinil: headache, anxiety, insomnia, appetite suppression, the rare-but-serious skin reactions (Stevens-Johnson), and reduced effectiveness of hormonal contraceptives. The later peak makes accidental sleep destruction MORE likely than with modafinil, not less — taken past mid-morning it will still be working at midnight.

• Anyone relying on hormonal contraception without adding a non-hormonal method
• Anyone with a history of serious drug rash, or who develops any rash on it
• Anyone with significant cardiovascular disease or uncontrolled hypertension
• Anyone with a history of psychosis, mania or bipolar disorder
• Anyone pregnant or breastfeeding

• Hormonal contraception — it induces CYP3A4 and can reduce the effectiveness of hormonal methods including pills, injections, implants, patches, rings and hormonal IUDs. The medication guide advises alternative or additional contraception during treatment and for a month after stopping. This causes real unintended pregnancies and is the single most consequential interaction.
• Other CYP3A4 substrates, where levels can fall — a long list including some immunosuppressants and antivirals, with the label specifically warning about reduced ciclosporin exposure.
• CYP2C19 substrates, where levels can RISE — the label names diazepam, phenytoin, propranolol, omeprazole and clomipramine.
• MAO inhibitors, where the label advises caution.
• Warfarin, where monitoring is advised.
• Caffeine and other stimulants, adding cardiovascular load and sleep disruption.

• Sleep — its long duration can worsen insomnia, and the label warns that wakefulness may not fully normalise: do not drive or do hazardous work until you know your own residual sleepiness on it.
• Any rash at all — a stop-and-seek-care event, not a wait-and-see one.
• Serious psychiatric symptoms, which are on the label and are not limited to low mood.
• Blood pressure and heart rate.
• For anyone using hormonal contraception, whether an additional non-hormonal method is in place.

The current label says physical dependence CAN occur, and that abrupt cessation or sharp reduction after chronic use can produce shaking, sweating, chills, gastrointestinal symptoms, confusion, aggression and atrial fibrillation, with postmarketing reports including convulsions and suicidality. Stopping after chronic use belongs with the prescriber, not a decision made alone. And anyone who has been using it daily to hold a work pattern together usually finds the underlying sleep problem was never addressed — that is the thing worth taking to a doctor.

US: Schedule IV prescription drug, same as modafinil.

Papers about this compound, not proof of the claims above. A title says what was studied, which is sometimes a negative result or a different question entirely.

• Modafinil/armodafinil for excessive daytime sleepiness after traumatic brain injury: a systematic review and meta-analysis
  Brain Inj, 2025
• Modafinil/armodafinil in obstructive sleep apnoea: a systematic review and meta-analysis
  Eur Respir J, 2016
• Armodafinil as a Potential Pharmacological Treatment for Attention Deficit Hyperactivity Disorder in Adults: A Review
  Curr Neuropharmacol, 2024

• Armodafinil2006
• ArmodafinilCNS Drugs · 2009
• Armodafinil as a Potential Pharmacological Treatment for Attention Deficit Hyperactivity Disorder in Adults: A ReviewCurr Neuropharmacol · 2024
• Armodafinil in MilkJ Hum Lact · 2023
• Modafinil/armodafinil for excessive daytime sleepiness after traumatic brain injury: a systematic review and meta-analysisBrain Inj · 2025
• Armodafinil in the treatment of excessive sleepinessExpert Opin Pharmacother · 2010
• Modafinil/armodafinil in obstructive sleep apnoea: a systematic review and meta-analysisEur Respir J · 2016
• Idiopathic Hypersomnia and Other Hypersomnia SyndromesNeurotherapeutics · 2021
• Headache improves with armodafinilJ Clin Sleep Med · 2024
• Armodafinil for excessive daytime sleepinessDrugs Today (Barc) · 2008
• Armodafinil (Nuvigil) for wakefulnessMed Lett Drugs Ther · 2010
• Interaction profile of armodafinil with medications metabolized by cytochrome P450 enzymes 1A2, 3A4 and 2C19 in healthy subjectsClin Pharmacokinet · 2008