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Side Effects


Modafinil has been evaluated for safety in over 3500 patients, of whom more than 2000 patients with excessive sleepiness associated with primary disorders of sleep and wakefulness were given at least one dose of modafinil. In clinical trials, modafinil has been found to be generally well tolerated and most adverse experiences were mild to moderate.

The most commonly observed adverse events ( ≥ 5%) associated with the use of PROVIGIL (modafinil) more frequently than placebo-treated patients in the placebo-controlled clinical studies in primary disorders of sleep and wakefulness were headache, nausea, nervousness, rhinitis, diarrhea, back pain, anxiety, insomnia, dizziness, and dyspepsia. The adverse event profile was similar across these studies.

In the placebo-controlled clinical trials, 74 of the 934 patients (8%) who received PROVIGIL (modafinil) discontinued due to an adverse experience compared to 3% of patients that received placebo. The most frequent reasons for discontinuation that occurred at a higher rate for PROVIGIL (modafinil) than placebo patients were headache (2%), nausea, anxiety, dizziness, insomnia, chest pain and nervousness (each < 1%). In a Canadian clinical trial, a 35 year old obese narcoleptic male with a prior history of syncopal episodes experienced a 9-second episode of asystole after 27 days of modafinil treatment (300 mg/day in divided doses).

Incidence in Controlled Trials

The following table (Table 3) presents the adverse experiences that occurred at a rate of 1% or more and were more frequent in adult patients treated with PROVIGIL (modafinil) than in placebo-treated patients in the principal, placebo-controlled clinical trials.

The prescriber should be aware that the figures provided below cannot be used to predict the frequency of adverse experiences in the course of usual medical practice, where patient characteristics and other factors may differ from those occurring during clinical studies. Similarly, the cited frequencies cannot be directly compared with figures obtained from other clinical investigations involving different treatments, uses, or investigators. Review of these frequencies, however, provides prescribers with a basis to estimate the relative contribution of drug and non-drug factors to the incidence of adverse events in the population studied.

Table 3: Incidence Of Treatment-Emergent Adverse Experiences In Parallel-Group, Placebo-Controlled Clinical Trials1 With PROVIGIL (modafinil) In Adults With Narcolepsy, OSA, and SWD (200mg, 300mg and 400mg)*

Body System Preferred Term Modafinil
(n = 934)
(n = 567)
Body as a Whole Headache 34% 23%
Back Pain 6% 5%
Flu Syndrome 4% 3%
Chest Pain 3% 1%
Chills 1% 0%
Neck Rigidity 1% 0%
Cardiovascular Hypertension 3% 1%
Tachycardia 2% 1%
Palpitation 2% 1%
Vasodilatation 2% 0%
Digestive Nausea 11% 3%
Diarrhea 6% 5%
Dyspepsia 5% 4%
Dry Mouth 4% 2%
Anorexia 4% 1%
Constipation 2% 1%
Abnormal Liver Function2 2% 1%
Flatulence 1% 0%
Mouth Ulceration 1% 0%
Thirst 1% 0%
Hemic/Lymphatic Eosinophilia 1% 0%
Metabolic/Nutritional Edema 1% 0%
Nervous Nervousness 7% 3%
Insomnia 5% 1%
Anxiety 5% 1%
Dizziness 5% 4%
Depression 2% 1%
Paresthesia 2% 0%
Somnolence 2% 1%
Hypertonia 1% 0%
Dyskinesia3 1% 0%
Hyperkinesia 1% 0%
Agitation 1% 0%
Confusion 1% 0%
Tremor 1% 0%
Emotional Lability 1% 0%
Vertigo 1% 0%
Respiratory Rhinitis 7% 6%
Pharyngitis 4% 2%
Lung Disorder 2% 1%
Epistaxis 1% 0%
Asthma 1% 0%
Skin/Appendages Sweating 1% 0%
Herpes Simplex 1% 0%
Special Senses Amblyopia 1% 0%
Abnormal Vision 1% 0%
Taste Perversion 1% 0%
Eye Pain 1% 0%
Urogenital Urine Abnormality 1% 0%
Hematuria 1% 0%
Pyuria 1% 0%
* Six double-blind, placebo-controlled clinical studies in narcolepsy, OSA, and SWD.
1 Events reported by at least 1% of patients treated with PROVIGIL (modafinil) that were more frequent than in the placebo group are included; incidence is rounded to the nearest 1%. The adverse experience terminology is coded using a standard modified COSTART Dictionary.
Events for which the PROVIGIL (modafinil) incidence was at least 1%, but equal to or less than placebo are not listed in the table. These events included the following: infection, pain, accidental injury, abdominal pain, hypothermia, allergic reaction, asthenia, fever, viral infection, neck pain, migraine, abnormal electrocardiogram, hypotension, tooth disorder, vomiting, periodontal abscess, increased appetite, ecchymosis, hyperglycemia, peripheral edema, weight loss, weight gain, myalgia, leg cramps, arthritis, cataplexy, thinking abnormality, sleep disorder, increased cough, sinusitis, dyspnea, bronchitis, rash, conjunctivitis, ear pain, dysmenorrhea4, urinary tract infection.
2 Elevated liver enzymes.
3 Oro-facial dyskinesias.
4 Incidence adjusted for gender.

Dose Dependency of Adverse Events

In the adult placebo-controlled clinical trials which compared doses of 200, 300, and 400 mg/day of PROVIGIL (modafinil) and placebo, the only adverse events that were clearly dose related were headache and anxiety.

Vital Sign Changes

While there was no consistent change in mean values of heart rate or systolic and diastolic blood pressure, the requirement for antihypertensive medication was slightly greater in patients on PROVIGIL compared to placebo (See PRECAUTIONS).

Weight Changes

There were no clinically significant differences in body weight change in patients treated with PROVIGIL (modafinil) compared to placebo-treated patients in the placebo-controlled clinical trials.

Laboratory Changes

Clinical chemistry, hematology, and urinalysis parameters were monitored in Phase 1, 2, and 3 studies. In these studies, mean plasma levels of gamma glutamyltransferase (GGT) and alkaline phosphatase (AP) were found to be higher following administration of PROVIGIL (modafinil) , but not placebo. Few subjects, however, had GGT or AP elevations outside of the normal range. Shifts to higher, but not clinically significantly abnormal, GGT and AP values appeared to increase with time in the population treated with PROVIGIL (modafinil) in the Phase 3 clinical trials. No differences were apparent in alanine aminotransferase, aspartate aminotransferase, total protein, albumin, or total bilirubin.

ECG Changes

No treatment-emergent pattern of ECG abnormalities was found in placebo-controlled clinical trials following administration of PROVIGIL (modafinil) .

Postmarketing Reports

The following adverse reactions have been identified during post-approval use of PROVIGIL (modafinil) . Because these reactions are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Decisions to include these reactions in labeling are typically based on one or more of the following factors: (1) seriousness of the reaction, (2) frequency of the reporting, or (3) strength of causal connection to PROVIGIL (modafinil) .

Hematologic: agranulocytosis

Drug Abuse And Dependence

Controlled Substance Class

Modafinil (PROVIGIL (modafinil) ) is listed in Schedule IV of the Controlled Substances Act.

Abuse Potential and Dependence

In addition to its wakefulness-promoting effect and increased locomotor activity in animals, in humans, PROVIGIL (modafinil) produces psychoactive and euphoric effects, alterations in mood, perception, thinking and feelings typical of other CNS stimulants. In in vitro binding studies, modafinil binds to the dopamine reuptake site and causes an increase in extracellular dopamine, but no increase in dopamine release. Modafinil is reinforcing, as evidenced by its self-administration in monkeys previously trained to self-administer cocaine. In some studies, modafinil was also partially discriminated as stimulant-like. Physicians should follow patients closely, especially those with a history of drug and/or stimulant (e.g., methylphenidate, amphetamine, or cocaine) abuse. Patients should be observed for signs of misuse or abuse (e.g., incrementation of doses or drug-seeking behavior).

The abuse potential of modafinil (200, 400, and 800 mg) was assessed relative to methylphenidate (45 and 90 mg) in an inpatient study in individuals experienced with drugs of abuse. Results from this clinical study demonstrated that modafinil produced psychoactive and euphoric effects and feelings consistent with other scheduled CNS stimulants (methylphenidate).


The effects of modafinil withdrawal were monitored following 9 weeks of modafinil use in one US Phase 3 controlled clinical trial. No specific symptoms of withdrawal were observed during 14 days of observation, although sleepiness returned in narcoleptic patients.

Read the Provigil (modafinil) Side Effects Center for a complete guide to possible side effects


CNS Active Drugs

Methylphenidate - In a single-dose study in healthy volunteers, simultaneous administration of modafinil (200 mg) with methylphenidate (40 mg) did not cause any significant alterations in the pharmacokinetics of either drug. However, the absorption of PROVIGIL (modafinil) may be delayed by approximately one hour when coadministered with methylphenidate.

In a multiple-dose, steady-state study in healthy volunteers, modafinil was administered once daily at 200 mg/day for 7 days followed by 400 mg/day for 21 days. Administration of methylphenidate (20 mg/day) during days 22-28 of modafinil treatment 8 hours after the daily dose of modafinil did not cause any significant alterations in the pharmacokinetics of modafinil.

Dextroamphetamine - In a single dose study in healthy volunteers, simultaneous administration of modafinil (200 mg) with dextroamphetamine (10 mg) did not cause any significant alterations in the pharmacokinetics of either drug. However, the absorption of PROVIGIL (modafinil) may be delayed by approximately one hour when coadministered with dextroamphetamine.

In a multiple-dose, steady-state study in healthy volunteers, modafinil was administered once daily at 200 mg/day for 7 days followed by 400 mg/day for 21 days. Administration of dextroamphetamine (20 mg/day) during days 22-28 of modafinil treatment 7 hours after the daily dose of modafinil did not cause any significant alterations in the pharmacokinetics of modafinil.

Clomipramine - The coadministration of a single dose of clomipramine (50 mg) on the first of three days of treatment with modafinil (200 mg/day) in healthy volunteers did not show an effect on the pharmacokinetics of either drug. However, one incident of increased levels of clomipramine and its active metabolite desmethylclomipramine has been reported in a patient with narcolepsy during treatment with modafinil.

Triazolam – In the drug interaction study between PROVIGIL (modafinil) and ethinyl estradiol (EE2), on the same days as those for the plasma sampling for EE2 pharmacokinetics, a single dose of triazolam (0.125 mg) was also administered. Mean Cmax and AUC0-&infin of triazolam were decreased by 42% and 59%, respectively, and its elimination half-life was decreased by approximately an hour after the modafinil treatment.

Monoamine Oxidase (MAO) Inhibitors - Interaction studies with monoamine oxidase inhibitors have not been performed. Therefore, caution should be used when concomitantly administering MAO inhibitors and modafinil.

Other Drugs

Warfarin - There were no significant changes in the pharmacokinetic profiles of R- and S- warfarin in healthy subjects given a single dose of racemic warfarin (5 mg) following chronic administration of modafinil (200 mg/day for 7 days followed by 400 mg/day for 27 days) relative to the profiles in subjects given placebo. However, more frequent monitoring of prothrombin times/INR is advisable whenever PROVIGIL is coadministered with warfarin (See CLINICAL PHARMACOLOGY, Pharmacokinetics, Drug-Drug Interactions).

Ethinyl Estradiol - Administration of modafinil to female volunteers once daily at 200 mg/day for 7 days followed by 400 mg/day for 21 days resulted in a mean 11% decrease in Cmax and 18% decrease in AUC0-24 of ethinyl estradiol (EE2; 0.035 mg; administered orally with norgestimate). There was no apparent change in the elimination rate of ethinyl estradiol.

Cyclosporine - One case of an interaction between modafinil and cyclosporine, a substrate of CYP3A4, has been reported in a 41 year old woman who had undergone an organ transplant. After one month of administration of 200 mg/day of modafinil, cyclosporine blood levels were decreased by 50%. The interaction was postulated to be due to the increased metabolism of cyclosporine, since no other factor expected to affect the disposition of the drug had changed. Dosage adjustment for cyclosporine may be needed.

Potential Interactions with Drugs That Inhibit, Induce, or are Metabolized by Cytochrome P-450 Isoenzymes and Other Hepatic Enzymes

In in vitro studies using primary human hepatocyte cultures, modafinil was shown to slightly induce CYP1A2, CYP2B6 and CYP3A4 in a concentration-dependent manner. Although induction results based on in vitro experiments are not necessarily predictive of response in vivo, caution needs to be exercised when PROVIGIL (modafinil) is coadministered with drugs that depend on these three enzymes for their clearance. Specifically, lower blood levels of such drugs could result (See Other Drugs, Cyclosporine above).

The exposure of human hepatocytes to modafinil in vitro produced an apparent concentration-related suppression of expression of CYP2C9 activity suggesting that there is a potential for a metabolic interaction between modafinil and the substrates of this enzyme (e.g., S-warfarin and phenytoin). In a subsequent clinical study in healthy volunteers, chronic modafinil treatment did not show a significant effect on the single-dose pharmacokinetics of warfarin when compared to placebo (See Other Drugs, Warfarin above).

In vitro studies using human liver microsomes showed that modafinil reversibly inhibited CYP2C19 at pharmacologically relevant concentrations of modafinil. CYP2C19 is also reversibly inhibited, with similar potency, by a circulating metabolite, modafinil sulfone. Although the maximum plasma concentrations of modafinil sulfone are much lower than those of parent modafinil, the combined effect of both compounds could produce sustained partial inhibition of the enzyme. Drugs that are largely eliminated via CYP2C19 metabolism, such as diazepam, propranolol, phenytoin (also via CYP2C9) or S-mephenytoin may have prolonged elimination upon coadministration with PROVIGIL (modafinil) and may require dosage reduction and monitoring for toxicity.

Tricyclic antidepressants - CYP2C19 also provides an ancillary pathway for the metabolism of certain tricyclic antidepressants (e.g., clomipramine and desipramine) that are primarily metabolized by CYP2D6. In tricyclic-treated patients deficient in CYP2D6 (i.e., those who are poor metabolizers of debrisoquine; 7-10% of the Caucasian population; similar or lower in other populations), the amount of metabolism by CYP2C19 may be substantially increased. PROVIGIL (modafinil) may cause elevation of the levels of the tricyclics in this subset of patients. Physicians should be aware that a reduction in the dose of tricyclic agents might be needed in these patients.

In addition, due to the partial involvement of CYP3A4 in the metabolic elimination of modafinil, coadministration of potent inducers of CYP3A4 (e.g., carbamazepine, phenobarbital, rifampin) or inhibitors of CYP3A4 (e.g., ketoconazole, itraconazole) could alter the plasma levels of modafinil.

Read the Provigil Drug Interactions Center for a complete guide to possible interactions

Last reviewed on RxList: 11/29/2010
This monograph has been modified to include the generic and brand name in many instances.

Side Effects

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