Prescription Drug Information: Modafinil (Page 3 of 6)

7 DRUG INTERACTIONS

Effects of Modafinil on CYP3A4/5 Substrates

The clearance of drugs that are substrates for CYP3A4/5 (e.g., steroidal contraceptives, cyclosporine, midazolam, and triazolam) may be increased by modafinil via induction of metabolic enzymes, which results in lower systemic exposure. Dosage adjustment of these drugs should be considered when these drugs are used concomitantly with modafinil [see Clinical Pharmacology (12.3)].

The effectiveness of steroidal contraceptives may be reduced when used with modafinil and for one month after discontinuation of therapy. Alternative or concomitant methods of contraception are recommended for patients taking steroidal contraceptives (e.g., ethinyl estradiol) when treated concomitantly with modafinil and for one month after discontinuation of modafinil treatment.

Blood levels of cyclosporine may be reduced when used with modafinil. Monitoring of circulating cyclosporine concentrations and appropriate dosage adjustment for cyclosporine should be considered when used concomitantly with modafinil.

Effects of Modafinil on CYP2C19 Substrates

Elimination of drugs that are substrates for CYP2C19 (e.g., phenytoin, diazepam, propranolol, omeprazole, and clomipramine) may be prolonged by modafinil via inhibition of metabolic enzymes, with resultant higher systemic exposure. In individuals deficient in the CYP2D6 enzyme, the levels of CYP2D6 substrates which have ancillary routes of elimination through CYP2C19, such as tricyclic antidepressants and selective serotonin reuptake inhibitors, may be increased by co-administration of modafinil. Dose adjustments of these drugs and other drugs that are substrates for CYP2C19 may be necessary when used concomitantly with modafinil [see Clinical Pharmacology (12.3)].

Warfarin

More frequent monitoring of prothrombin times/INR should be considered whenever modafinil is coadministered with warfarin [see Clinical Pharmacology (12.3)].

Monoamine Oxidase (MAO) Inhibitors

Caution should be used when concomitantly administering MAO inhibitors and modafinil.

8 USE IN SPECIFIC POPULATIONS

8.1 Pregnancy

Teratogenic Effects

Pregnancy Category C

There are no adequate and well-controlled studies of modafinil in pregnant women. Intrauterine growth restriction and spontaneous abortion have been reported in association with modafinil (a mixture of R- and S-modafinil) and armodafinil (the R-enantiomer of modafinil). Although the pharmacology of modafinil is not identical to that of the sympathomimetic amines, it does share some pharmacologic properties with this class. Certain of these drugs have been associated with intrauterine growth restriction and spontaneous abortions. Whether the cases reported with modafinil are drug-related is unknown. In studies of modafinil and armodafinil conducted in rats (modafinil, armodafinil) and rabbits (modafinil), developmental toxicity was observed at clinically relevant plasma exposures. Modafinil should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Modafinil (50, 100, or 200 mg/kg/day) administered orally to pregnant rats throughout organogenesis caused, in the absence of maternal toxicity, an increase in resorptions and an increased incidence of visceral and skeletal variations in the offspring at the highest dose tested. The higher no-effect dose for embryofetal developmental toxicity in rats (100 mg/kg/day) was associated with a plasma modafinil AUC less than that in humans at the recommended human dose (RHD) of modafinil (200 mg/day). However, in a subsequent study of up to 480 mg/kg/day of modafinil, no adverse effects on embryofetal development were observed. Oral administration of armodafinil (60, 200, or 600 mg/kg/day) to pregnant rats throughout organogenesis resulted in increased incidences of fetal visceral and skeletal variations and decreased fetal body weight at the highest dose tested. The highest no-effect dose for embryofetal developmental toxicity in rats (200 mg/kg/day) was associated with a plasma armodafinil AUC less than that in humans at the RHD of modafinil.

Modafinil administered orally to pregnant rabbits throughout organogenesis at doses of up to 100 mg/kg/day had no effect on embryofetal development; however, the doses used were too low to adequately assess the effects of modafinil on embryofetal development. In a subsequent developmental toxicity study evaluating doses of 45, 90, and 180 mg/kg/day in pregnant rabbits, the incidences of fetal structural alterations and embryofetal death were increased at the highest dose. The highest no-effect dose for developmental toxicity (100 mg/kg/day) was associated with a plasma modafinil AUC similar to that in humans at the RHD of modafinil.

Modafinil administration to rats throughout gestation and lactation at oral doses of up to 200 mg/kg/day resulted in decreased viability in the offspring at doses greater than 20 mg/kg/day, a dose resulting in a plasma modafinil AUC less than that in humans at the RHD of modafinil. No effects on postnatal developmental and neurobehavioral parameters were observed in surviving offspring.

8.3 Nursing Mothers

It is not known whether modafinil or its metabolites are excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when modafinil is administered to a nursing woman.

8.4 Pediatric Use

Safety and effectiveness in pediatric patients have not been established. Modafinil is not approved in this population for any indication.

Serious skin rashes, including erythema multiforme major (EMM) and Stevens-Johnson Syndrome (SJS) have been associated with modafinil use in pediatric patients [see Warnings and Precautions (5.1)].

In a controlled 6 week study, 165 pediatric patients (aged 5 to 17 years) with narcolepsy were treated with modafinil (n=123), or placebo (n=42). There were no statistically significant differences favoring modafinil over placebo in prolonging sleep latency as measured by MSLT, or in perceptions of sleepiness as determined by the clinical global impression-clinician scale (CGI-C).

In the controlled and open-label clinical studies, treatment emergent adverse reactions of the psychiatric and nervous system included Tourette’s syndrome, insomnia, hostility, increased cataplexy, increased hypnagogic hallucinations, and suicidal ideation. Transient leukopenia, which resolved without medical intervention, was also observed. In the controlled clinical study, 3 of 38 girls, ages 12 or older, treated with modafinil experienced dysmenorrhea compared to 0 of 10 girls who received placebo.

There were three 7 to 9 week, double-blind, placebo-controlled, parallel group studies in children and adolescents (aged 6 to 17 years) with Attention-Deficit Hyperactivity Disorder (ADHD). Two of the studies were flexible-dose studies (up to 425 mg/day), and the third was a fixed-dose study (340 mg/day for patients <30 kg and 425 mg/day for patients ≥30 kg). Although these studies showed statistically significant differences favoring modafinil over placebo in reducing ADHD symptoms as measured by the ADHD-RS (school version), there were 3 cases of serious rash including one case of possible SJS among 933 patients exposed to modafinil in this program. Modafinil is not approved for use in treating ADHD.

8.5 Geriatric Use

In clinical trials, experience in a limited number of modafinil-treated patients who were greater than 65 years of age showed an incidence of adverse reactions similar to other age groups. In elderly patients, elimination of modafinil and its metabolites may be reduced as a consequence of aging. Therefore, consideration should be given to the use of lower doses and close monitoring in this population [see Dosage and Administration (2.4) and Clinical Pharmacology (12.3)].

8.6 Hepatic Impairment

In patients with severe hepatic impairment, the dose of modafinil should be reduced to one-half of that recommended for patients with normal hepatic function [see Dosage and Administration (2.3) and Clinical Pharmacology (12.3)].

9 DRUG ABUSE AND DEPENDENCE

9.1 Controlled Substance

Modafinil tablets contain modafinil, a Schedule IV controlled substance.

9.2 Abuse

In humans, modafinil produces psychoactive and euphoric effects, alterations in mood, perception, thinking, and feelings typical of other CNS stimulants. In in vitr o 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).

9.3 Dependence

In one placebo-controlled clinical trial, the effects of modafinil withdrawal were monitored following 9 weeks of modafinil use. There were no reported withdrawal symptoms with modafinil during 14 days of observation, although sleepiness returned in narcoleptic patients.

10 OVERDOSAGE

In clinical trials, a total of 151 protocol-specified doses ranging from 1000 to 1600 mg/day (5 to 8 times the recommended daily dose of modafinil) have been administered to 32 subjects, including 13 subjects who received doses of 1000 or 1200 mg/day for 7 to 21 consecutive days. In addition, several intentional acute overdoses occurred; the two largest being 4500 mg and 4000 mg taken by two subjects participating in foreign depression studies. None of these study subjects experienced any unexpected or life-threatening effects. Adverse reactions that were reported at these doses included excitation or agitation, insomnia, and slight or moderate elevations in hemodynamic parameters. Other observed high-dose effects in clinical studies have included anxiety, irritability, aggressiveness, confusion, nervousness, tremor, palpitations, sleep disturbances, nausea, diarrhea, and decreased prothrombin time. From postmarketing experience, there have been reports of fatal overdoses involving modafinil alone or in combination with other drugs. Symptoms most often accompanying modafinil overdose, alone or in combination with other drugs have included insomnia; central nervous system symptoms such as restlessness, disorientation, confusion, agitation, anxiety, excitation, and hallucination; digestive changes such as nausea and diarrhea; and cardiovascular changes such as tachycardia, bradycardia, hypertension, and chest pain. Cases of accidental ingestion/overdose have been reported in children as young as 11 months of age. The highest reported accidental ingestion on a mg/kg basis occurred in a three-year-old boy who ingested 800 to 1000 mg (50 to 63 mg/kg) of modafinil. The child remained stable. The symptoms associated with overdose in children were similar to those observed in adults. No specific antidote exists for the toxic effects of a modafinil overdose. Such overdoses should be managed with primarily supportive care, including cardiovascular monitoring.

11 DESCRIPTION

Modafinil, USP is wakefulness-promoting agent for oral administration. Modafinil, USP is a racemic compound. The chemical name for modafinil, USP is 2-[(diphenylmethyl)sulfinyl]acetamide. The molecular formula is C15 H15 NO2 S and the molecular weight is 273.35.

The chemical structure is:

chemical structure
(click image for full-size original)

Modafinil, USP is a white to off-white, crystalline powder that is practically insoluble in water and cyclohexane. It is sparingly to slightly soluble in methanol and acetone.

Modafinil tablets, USP contain 100 mg or 200 mg of modafinil, USP and the following inactive ingredients: colloidal silicon dioxide, crospovidone, lactose monohydrate, magnesium stearate, microcrystalline cellulose, povidone, pregelatinized starch, and talc.

USP dissolution test pending.

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