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 Modafinil. If you are concerned about side effects, discuss the risks and benefits of Modafinil with your doctor.

The following side effects have been reported by at least 1% of people taking Modafinil. 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
• headache
• nausea
• 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:

• increased blood pressure
• increased heart rate or palpitations
• agitation
• dizziness or fainting
• mood swings
• 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)
• skin rash

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

• chest pain
• signs of Anaphylaxis (severe allergic reaction) (such as swelling of face, eyes, lips, tongue; difficulty swallowing or breathing; hoarseness; chest tightness)
• signs of severe skin reaction (blistering rash with Fever, sores in mouth, peeling skin)

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 Modafinil.

Each white, round, biconvex tablet, engraved "MOD" over "100" on one side, contains modafinil 100 mg. Nonmedicinal ingredients: methylcellulose, croscarmellose sodium, magnesium stearate, and colloidal silicon dioxide.

Do not take Modafinil if you:

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

There may be an interaction between modafinil and any of the following:

• alcohol
• alpha blockers (e.g., Alfuzosin, Doxazosin, Silodosin, Tamsulosin)
• Amiodarone
• amphetamines (e.g., Dextroamphetamine, Lisdexamfetamine)
• anti-cancer medications (e.g., Cabazitaxel, Docetaxel; Doxorubicin; Etoposide, Ifosfamide, Irinotecan, Vincristine)
• antipsychotics (e.g., Aripiprazole, Clozapine, Haloperidol, Quetiapine), Aprepitant
• Atomoxetine
• "azole" antifungals (e.g., itraconazole, ketoconazole, posaconazole, Voriconazole)
• benzodiazepines (e.g., Chlordiazepoxide, Clonazepam, Diazepam, Lorazepam)
• birth control pills
• Bisoprolol
• Bosentan
• fast acting bronchodilators (e.g., salbutamol, terbutaline)
• long acting bronchodilators (e.g., formoterol, salmeterol)
• Buprenorphine
• Buspirone
• caffeine
• Calcitriol
• calcium channel blockers (e.g., Amlodipine, Diltiazem, Nifedipine, Verapamil)
• cannabis
• Carbamazepine
• chloroquine
• conivaptan
• Cyclosporine
• Dantrolene
• Dapsone
• decongestant cold medications (e.g., phenylephrine, Pseudoephedrine)
• decongestant eye drops and nose sprays (e.g., naphazoline, oxymetazoline, xylometazoline)
• Deferasirox
• Dexamethasone
• dipivefrin
• Disopyramide
• Enzalutamide
• Epinephrine
• estrogens (e.g., conjugated estrogen, Estradiol, ethinyl estradiol)
• Everolimus
• Fentanyl
• "gliptin" Diabetes medications (e.g., Linagliptin, Saxagliptin, Sitagliptin)
• Guanfacine
• Hepatitis C antivirals (e.g., daclatasvir, dasabuvir, ledipasvir, paritaprevir, ombitasvir, sofosbuvir)
• HIV non-nucleoside reverse transcriptase  inhibitors (NNRTIs; e.g., delavirdine, efavirenz, etravirine, nevirapine)
• HIV protease inhibitors (e.g., atazanavir, indinavir, ritonavir, saquinavir)
• Hydrocodone
• lidocaine
• Linezolid
• Losartan
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• maraviroc
• Mefloquine
• Methadone
• Methylphenidate
• mifepristone
• Mirtazapine
• Moclobemide
• Montelukast
• Nabilone
• nefazodone
• nitrates (e.g., isosorbide dinitrate,  isosorbide mononitrate)
• Ondansetron
• Oxcarbazepine
• Oxycodone
• Perampanel
• Phenobarbital
• Phenytoin
• praziquantel
• Primaquine
• primidone
• progestins (e.g., Dienogest, Levonorgestrel, medroxyprogesterone, Norethindrone)
• protein kinase inhibitors (e.g., Dasatinib, imatinib, Nilotinib, Pazopanib)
• proton pump inhibitors (e.g., Lansoprazole, Omeprazole)
• quinidine
• quinine
• Repaglinide
• rifabutin
• rifampin
• rilpivirine
• Rivaroxaban
• Romidepsin
• St. John's wort
• selective serotonin reuptake inhibitors (SSRIs; e.g., Citalopram, Fluoxetine, Paroxetine, Sertraline)
• Sildenafil
• siltuximab
• Sirolimus
• "statin" anti-cholesterol medications (e.g., Atorvastatin, Lovastatin, Simvastatin)
• Tacrolimus
• Tamoxifen
• Tetracycline
• Theophylline (e.g., Aminophylline, Oxtriphylline, theophylline)
• Ticagrelor
• Ticlopidine
• Tocilizumab
• Tofacitinib
• Tolterodine
• Tolvaptan
• Tramadol
• Trazodone
• tricyclic antidepressants (e.g., Amitriptyline, Clomipramine, Imipramine)
• Trimethoprim
• Venlafaxine
• Zolpidem
• zonisamide
• Zopiclone

If you are taking any of these 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.

Medications other than those listed above may interact with Modafinil. 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.

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 Modafinil.

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 1 month 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 Modafinil 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. If you have a heart condition or history of heart problems, discuss with your doctor how Modafinil may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Modafinil, 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.

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 Modafinil may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Modafinil, 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 Modafinil may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Modafinil, 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 Modafinil, contact your doctor immediately. Your doctor will monitor you closely for these side effects while you are taking Modafinil.

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.

Seizure disorder: If you have a seizure disorder or a history of seizures, discuss with your doctor how Modafinil may affect your medical condition, how your medical condition may affect the dosing and effectiveness of Modafinil, and whether any special monitoring is needed.

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, sores on the lips or eyes or covers a large area of the body, contact your doctor immediately.

Pregnancy: Modafinil should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking Modafinil, contact your doctor immediately.

Breast-feeding: It is not known if modafinil passes into breast milk. If you are a breast-feeding mother and are taking Modafinil, 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.

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.

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

Your doctor may have suggested Modafinil 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 Modafinil, speak to your doctor. Do not stop taking Modafinil without consulting your doctor.

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