Safety
Modafinil and armodafinil side effects and dosage
The most common side effect of modafinil and armodafinil is headache, followed by nausea, nervousness or anxiety, dizziness and trouble sleeping. Serious reactions are rare: stop and get medical help if you get a rash, swelling, trouble breathing, chest pain or changes in mood.
Both can make hormonal birth control less effective. The usual dose is 200 mg of modafinil or 150 mg to 250 mg of armodafinil, once a day in the morning. Talk to a doctor before you start.
- Headache is the most common
- Stop at the first rash
- Birth control may fail
- Avoid alcohol
Updated
Common side effects
These are the side effects seen more often than on placebo in the US trials, from the official labels. The figure in brackets is the rate on placebo. The two medicines were tested in separate trials, so compare each with its own placebo, not with each other.
| Modafinil | Armodafinil | |
|---|---|---|
| Headache | 34% (23%) | 17% (9%) |
| Nausea | 11% (3%) | 7% (3%) |
| Nervousness | 7% (3%) | 1% (0%) |
| Anxiety | 5% (1%) | 4% (1%) |
| Trouble sleeping | 5% (1%) | 5% (1%) |
| Dizziness | 5% (4%) | 5% (2%) |
| Diarrhoea | 6% (5%) | 4% (2%) |
| Dry mouth | 4% (2%) | 4% (1%) |
| Indigestion | 5% (4%) | 2% (0%) |
| Stopped because of a side effect | 8% (3%) | 7% (4%) |
Headache and anxiety were more common at higher doses of modafinil. With armodafinil, headache, rash, depression, dry mouth, trouble sleeping and nausea were more common at 250 mg than at 150 mg.
Serious side effects
Stop taking it and get medical help straight away if you get any of these.
- A rash, mouth sores, blisters or peeling skin. Rare serious skin reactions, including Stevens-Johnson syndrome, have been reported. Stopping at the first sign matters.
- An allergic reaction: swelling of the face, eyes, lips, tongue or throat, hives, hoarseness, or trouble swallowing or breathing.
- Fever, swollen glands and a rash together, which can mean a reaction that affects organs such as the liver.
- Changes in mood or thinking: depression, anxiety, mania, hallucinations, aggression or thoughts of suicide.
- Chest pain, a racing or uneven heartbeat.
Who should not take modafinil or armodafinil
Do not take either if you have had an allergic reaction to modafinil or armodafinil. Talk to a doctor first if any of these apply:
- You are under 17. Neither is approved for children, and serious rashes were seen in child trials of modafinil.
- You have heart disease, high blood pressure, or a history of left ventricular hypertrophy, or of mitral valve problems with stimulants.
- You have had psychosis, depression or mania.
- You have liver or kidney problems.
- You have ever misused or depended on alcohol, prescription medicines or street drugs.
- You are pregnant, planning a pregnancy or breastfeeding.
Birth control and pregnancy
Modafinil and armodafinil speed up how the body clears some hormones. That can make hormonal birth control fail: the pill, the patch, the ring, the implant, the injection and hormonal coils.
- The US labels say to use a barrier or non-hormonal method as well, while you take them and for one month after you stop.
- The UK medicines regulator (MHRA) says to use effective contraception while taking modafinil and for two months after stopping, and not to use modafinil during pregnancy, because of a possible higher risk of birth defects.
If you could become pregnant, talk to a doctor about which method suits you before you start.
Other medicines and alcohol
Tell a doctor or pharmacist about everything you take. The labels name these interactions:
- Hormonal birth control and ciclosporin: lower levels, so they may work less well.
- Omeprazole, phenytoin and diazepam: higher levels, so their side effects may be stronger.
- Warfarin: your clotting tests may need checking more often.
- MAO inhibitor antidepressants: to be used together only with care.
Alcohol: taking modafinil or armodafinil with alcohol has not been studied, and the labels say it is wise to avoid it.
Dosage
| Modafinil | Armodafinil | |
|---|---|---|
| Narcolepsy or sleep apnea | 200 mg once a day, in the morning | 150 mg to 250 mg once a day, in the morning |
| Shift work disorder | 200 mg about 1 hour before the shift | 150 mg about 1 hour before the shift |
| Higher doses | Up to 400 mg tolerated, no consistent extra benefit | 250 mg in sleep apnea, no consistent extra benefit over 150 mg |
| Severe liver problems | Half the usual dose | A lower dose |
| Older adults | A lower dose may be considered | A lower dose may be considered |
Both are taken once a day, in the morning or before a shift, and trouble sleeping is one of their common side effects. A doctor sets the dose that is right for you.
Dependence, driving and sleep
In the US both are Schedule IV controlled substances, because they can be misused or lead to dependence. In one trial, people who stopped modafinil after 9 weeks had no withdrawal symptoms over 14 days, but sleepiness came back in people with narcolepsy.
Neither replaces sleep. The labels say not to drive or do anything risky until you know how the medicine affects you, and to keep using any treatment you already have, such as CPAP for sleep apnea.
Looking for brands and prices? See modafinil and armodafinil.
Questions and answers
What are the most common side effects of modafinil?
In the US trials the most common side effects of modafinil were headache, nausea, nervousness, a runny or blocked nose, back pain, diarrhoea, anxiety, dizziness, indigestion and trouble sleeping. Headache was the most common by far: 34% of people on modafinil against 23% on placebo.
What are the side effects of armodafinil?
The most common side effects of armodafinil in the US trials were headache, nausea, dizziness and trouble sleeping, followed by anxiety, diarrhoea and dry mouth. Its serious warnings are the same as for modafinil.
Does modafinil stop birth control from working?
It can. Modafinil and armodafinil can make hormonal birth control, such as the pill, patch, ring, implant or injection, less effective while you take them and for one month after you stop, according to the US labels. UK guidance says to use effective contraception for two months after stopping modafinil. Use a condom or a non-hormonal method as well, and ask a doctor.
Can I drink alcohol with modafinil?
Taking modafinil or armodafinil with alcohol has not been studied. The US labels say it is wise to avoid alcohol while you take them.
What is the maximum dose of modafinil?
The US label dose is 200 mg once a day. Doses up to 400 mg a day were well tolerated in trials, but gave no consistent extra benefit over 200 mg. For armodafinil the label dose is 150 mg to 250 mg a day.
Is modafinil addictive?
Modafinil and armodafinil are Schedule IV controlled substances in the US because they can be misused or lead to dependence. In one trial, people who stopped modafinil after 9 weeks had no withdrawal symptoms over the next 14 days, though sleepiness came back in people with narcolepsy.
Can modafinil cause a rash?
Yes, and rarely the rash can be serious, including Stevens-Johnson syndrome. Stop taking it and get medical help at the first sign of a rash, mouth sores, blisters or peeling skin, unless the rash is clearly caused by something else.
Can I take modafinil while pregnant?
No, unless a doctor decides otherwise. The UK medicines regulator says modafinil should not be used during pregnancy because of a possible higher risk of birth defects, and the US label says it should be used only if the benefit justifies the risk.
Sources
Medical facts on this page come from these official labels, regulators and studies.
- US FDA: Provigil (modafinil) prescribing information, revised January 2015
- US FDA: Nuvigil (armodafinil) prescribing information, revised February 2017
- UK MHRA Drug Safety Update, November 2020: modafinil and the risk of birth defects
- European Medicines Agency: review of modafinil medicines, 2010 to 2011