Modafinil belongs to the group of medicines known as central nervous system (CNS) stimulants. It prevents sleepiness by stimulating certain parts of the brain. It is used to help people with a condition called narcolepsy, which causes daytime excessive sleepiness, by preventing drowsiness and keeping these people from falling asleep.

It is also used to reduce excessive daytime sleepiness for people with obstructive sleep apnea or hypopnea syndrome (breathing disorder that happens while sleeping), shift-work sleep disorder, or circadian rhythm sleep disorder.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

The recommended adult dose of modafinil for narcolepsy is between 200 mg and 400 mg daily. The total daily dose is usually divided between a morning and noon dose. Doses are usually started at 200 mg per day, and then gradually increased by the doctor as needed to a maximum of 400 mg daily.

For adults with obstructive sleep apnea, the usual adult daily dose of modafinil is 200 mg taken as a single dose in the morning.

Adults with shift work disorder should take 200 mg once daily, approximately 1 hour before the start of the work shift.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way you are using the medication without talking to your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Avoid taking the medication in the late afternoon or evening, as it may prevent falling asleep at your normal bedtime. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Each white-to-off-white, capsule-shaped, biconvex, uncoated tablet, with "M 100" debossed on one side and plain on other side, contains 100 mg of modafinil. Nonmedicinal ingredients: lactose monohydrate, microcrystalline cellulose, crospovidone, povidone, mannitol, and magnesium stearate.

Do not take this medication if you:

• are allergic to modafinil or any ingredients of the medication
• are in an agitated state
• have severe anxiety
• are or may become pregnant

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• anxiety
• back pain
• diarrhea
• dizziness
• drowsiness
• nervousness
• sleeping difficulties
• stuffy or runny nose
• upset stomach

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• hallucinations (e.g., hearing or seeing things that are not there)
• increased blood pressure
• irregular heart rate or palpitations
• ongoing sleepiness
• signs of depression (such as such as feeling sad, losing interest in things you used to enjoy, weight changes, changes in sleep habits, feelings of guilt or worthlessness, thoughts of self-harm)
• signs of infection (symptoms may include fever or chills, shortness of breath, sore throat)
• symptoms of mania (e.g., extreme increase in activity, talking, energy)

Stop taking the medication and seek immediate medical attention if any of the following occur:

• chest pain
• signs of a severe allergic reaction (such as swelling of face, eyes, lips, tongue; difficulty swallowing or breathing; hoarseness; chest tightness)
• signs of a heart attack (e.g., sudden chest pain or pain radiating to back, down arm, jaw; sensation of fullness of the chest; nausea; vomiting; sweating; anxiety)
• signs of a severe skin reaction (blistering rash with fever, sores in mouth, peeling skin) with or without swollen glands, yellowing skin or eyes, dry cough, thirst, decreased urine production
• signs of a stroke (e.g., sudden or severe headache; sudden loss of coordination; vision changes; sudden slurring of speech; or unexplained weakness, numbness, or pain in arm or leg)
• thoughts of self-harm or suicide

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin taking a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should take this medication.

Alcohol and other medications that cause drowsiness: Do not combine this medication with alcohol or other medications that cause drowsiness (e.g., antidepressants, sleeping pills, anxiety medications) because modafinil can also cause drowsiness, and the combination can be dangerous.

Birth control: Birth control pills, patches, and other forms of estrogen and estrogen/progestin birth control may be less effective when you are also taking modafinil. Alternative methods of birth control should be used while you are taking modafinil and for at least 2 months after stopping treatment with modafinil.

Drowsiness/reduced alertness: Some people experience ongoing drowsiness or dizziness while taking modafinil. It may also cause overconfidence and over-stimulation, causing poor judgement. Do not drive, operate machinery, or perform other hazardous tasks until you have determined how this medication affects you.

Heart disease: Modafinil may cause an irregular heartbeat or increased blood pressure. The safety of using modafinil has not been established for people with heart problems. Your doctor may order an electrocardiogram (ECG), a test that measures heart rate and rhythm, before starting and during treatment with modafinil. If you have a heart condition or history of heart problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Hypersensitivity syndrome: A severe allergic reaction called hypersensitivity syndrome has occurred for some people with the use of modafinil. Stop taking the medication and get immediate medical attention if you have symptoms of a severe allergic reaction, including fever, swollen glands, yellowing of the skin or eyes, or flu-like symptoms with skin rash or blistering.

Kidney function: If you have kidney disease or decreased kidney function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: People with severe liver disease should take lower doses of modafinil because of an increased risk of accumulation of the medication in the body and side effects. If you have liver disease or decreased liver function, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Mental illness: Modafinil may reactivate certain mental disorders or cause confusion and agitation. If you have a history of mental disorders such as depression, psychosis, or mania, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed. If you experience symptoms of agitation, depression, or hallucination, or notice them in a family member who is taking this medication, contact your doctor immediately. Your doctor will monitor you closely for these side effects while you are taking this medication.

Normal fatigue states: Modafinil should not be used to treat normal fatigue states (e.g., fatigue due to lack of sleep rather than narcolepsy), as it can lead to overconfidence in abilities without actually increasing performance. This could make it more dangerous to perform certain activities.

Skin rash: Modafinil may cause skin rash. Rarely, people taking modafinil experience a severe skin reaction that can be life-threatening. This usually occurs within the first 5 weeks of taking the medication, but it can develop at any time while you are taking modafinil. If you experience a rash that gets worse, or develops into blisters or sores on the lips or eyes or covers a large area of the body, contact your doctor immediately.

Pregnancy: This medication may cause harm to an unborn baby and should not be used during pregnancy. If you become pregnant while taking this medication, contact your doctor immediately. People who could become pregnant who are taking modafinil should use an effective method of birth control during treatment and for 8 weeks after stopping modafinil. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: It is not known if modafinil passes into breast milk. If you are breast-feeding and taking this medication, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Children: Serious reactions have been associated with the use of modafinil by children. The risks and benefits of modafinil have not been established for children. It is not recommended that children be given modafinil.

Seniors: Seniors may be more sensitive to the effects of modafinil. They should use lower starting doses.

For a full list of interactions, use the Drug Interaction Checker available on the Drugs.com website.

If you are taking other medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.