RUFINAMIDE: 871 Adverse Event Reports & Safety Profile

BANZEL (rufinamide) is a triazole derivative structurally unrelated to currently marketed antiepileptic drugs (AEDs). Rufinamide has the chemical name 1-[(2,6-difluorophenyl)methyl]-1 H -1,2,3-triazole-4 carboxamide. It has an empirical formula of C 10 H 8 F 2 N 4 O and a molecular weight of 238.2. The drug substance is a white, crystalline, odorless, and slightly bitter tasting neutral powder. Rufinamide is practically insoluble in water, slightly soluble in tetrahydrofuran and in methanol, and very slightly soluble in ethanol and in acetonitrile. BANZEL is available for oral administration in film-coated tablets, scored on both sides, containing 200 and 400 mg of rufinamide. Inactive ingredients are colloidal silicon dioxide, corn starch crosscarmellose sodium, hypromellose, lactose monohydrate, magnesium stearate, microcrystalline cellulose, and sodium lauryl sulphate. The film coating contains hypromellose, iron oxide red, polyethylene glycol, talc, and titanium dioxide. BANZEL is also available for oral administration as a liquid containing rufinamide at a concentration of 40 mg/mL. Inactive ingredients include microcrystalline cellulose and carboxymethylcellulose sodium, hydroxyethylcellulose, anhydrous citric acid, simethicone emulsion 30%, poloxamer 188, methylparaben, propylparaben, propylene glycol, potassium sorbate, noncrystallizing sorbitol solution 70%, and an orange flavor. BANZEL (rufinamide)

AND USAGE Rufinamide oral suspension is indicated for adjunctive treatment of seizures associated with Lennox-Gastaut Syndrome in pediatric patients 1 year of age and older and in adults. Rufinamide oral suspension is indicated for adjunctive treatment of seizures associated with Lennox-Gastaut Syndrome (LGS) in pediatric patients 1 year of age and older, and in adults ( 1 )

AND ADMINISTRATION Rufinamide oral suspension should be given with food ( 2.2 ) Measure oral suspension using provided adapter and dosing syringe ( 2.2 ) Pediatric patients 1 year and older: Starting daily dose: 10 mg/kg per day in two equally divided doses ( 2.1 ) Increase by 10 mg/kg increments every other day to maximum dose of 45 mg/kg per day, not to exceed 3,200 mg per day, in two divided doses ( 2.1 ) Adults: Starting daily dose: 400 mg to 800 mg per day in two equally divided doses ( 2.1 ) Increase by 400 mg to 800 mg every other day until a maximum dose of 3,200 mg per day, in two divided doses, is reached ( 2.1 )

2.1 Dosage Information Pediatric patients ( 1 year to less than 17 years) The recommended starting daily dose of rufinamide oral suspension in pediatric patients with Lennox-Gastaut Syndrome is approximately 10 mg/kg administered in two equally divided doses. The dose should be increased by approximately 10 mg/kg increments every other day until a maximum daily dose of 45 mg/kg, not to exceed 3,200 mg, administered in two equally divided doses, is reached. It is not known whether doses lower than the target doses are effective. Adults (17 years and older) The recommended starting daily dose of rufinamide oral suspension in adults with Lennox-Gastaut Syndrome is 400 mg to 800 mg per day administered in two equally divided doses. The dose should be increased by 400 mg to 800 mg every other day until a maximum daily dose of 3,200 mg, administered in two equally divided doses, is reached. It is not known whether doses lower than 3,200 mg are effective.

2.2 Administration Information Administer rufinamide oral suspension with food. Rufinamide oral suspension should be shaken well before every administration. The provided adapter and calibrated oral dosing syringe should be used to administer the oral suspension. The adapter which is supplied in the product carton should be inserted firmly into the neck of the bottle before use and remain in place for the duration of the usage of the bottle. The dosing syringe should be inserted into the adapter and the dose withdrawn from the inverted bottle. The cap should be replaced after each use. The cap fits properly when the adapter is in place <span class="opacity-50 text-xs">[see Patient Counseling Information ( 17 )]</span> .

2.3 Dosing in Patients Undergoing Hemodialysis Hemodialysis may reduce exposure to a limited (about 30%) extent. Accordingly, adjusting the rufinamide oral suspension dose during the dialysis process should be considered [ s ee Clinical Pharmacology ( 12.3 ) ] .

2.4 Dosing in Patients with Hepatic Disease Use of rufinamide oral suspension in patients with hepatic impairment has not been studied. Therefore, use in patients with severe hepatic impairment is not recommended. Caution should be exercised in treating patients with mild to moderate hepatic impairment [ see Use in Specific Population s ( 8.7 ) ] .

2.5 Dosing in Patients Taking Valproate Patients taking valproate should begin rufinamide oral suspension at a dose lower than 10 mg/kg per day in pediatric patients or 400 mg per day in adults [ see Drug Int eractions ( 7.2 ) ] .

Rufinamide oral suspension is contraindicated in patients with Familial Short QT syndrome [see Warnings and Precautions ( 5.3 )] . Rufinamide oral suspension is contraindicated in patients with Familial Short QT syndrome ( 4 )

REACTIONS The following serious adverse reactions are described below and elsewhere in the labeling: Suicidal Behavior and Ideation [see Warnings and Precautions (5.1) ]

Central Nervous System

Reactions [see Warnings and Precautions (5.2) ] QT Shortening [see Warnings and Precautions (5.3) ] Multi-Organ Hypersensitivity/Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) [see Warnings and Precautions (5.4) ] Leukopenia [see Warnings and Precautions (5.7) ] Most common adverse reactions (≥10% and greater than placebo) were headache, dizziness, fatigue, somnolence, and nausea ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Micro Labs USA, Inc. at 1-855-839-8195 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch .

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adverse

Reactions in Adult and Pediatric Patients ages 3 to 17 years of age In the pooled, double-blind, adjunctive therapy studies in adult and pediatric patients ages 3 to 17 years of age, the most common (≥10%) adverse reactions in rufinamide tablet-treated patients, in all doses studied (200 to 3200 mg per day) with a higher frequency than in patients on placebo were: headache, dizziness, fatigue, somnolence, and nausea.

Table

2 lists adverse reactions that occurred in at least 3% of pediatric patients (ages 3 to less than 17 years) with epilepsy treated with rufinamide tablets in controlled adjunctive studies and were numerically more common in patients treated with rufinamide tablets than in patients on placebo. At the target dose of 45 mg/kg per day for adjunctive therapy in pediatric patients (ages 3 to less than 17 years), the most common (≥3%) adverse reactions with an incidence greater than in placebo for rufinamide tablets were somnolence, vomiting, and headache.

Table

2: Adverse Reactions in Pediatric Patients (Ages 3 to less than 17 years) in Pooled Double-Blind Adjunctive Trials Adverse Reaction Rufinamide Tablet (N=187)% Placebo (N=182)% Somnolence 17 9 Vomiting 17 7 Headache 16 8 Fatigue 9 8 Dizziness 8 6 Nausea 7 3 Influenza 5 4 Nasopharyngitis 5 3 Decreased Appetite 5 2 Rash 4 2 Ataxia 4 1 Diplopia 4 1 Bronchitis 3 2 Sinusitis 3 2 Psychomotor Hyperactivity 3 1 Upper Abdominal Pain 3 2 Aggression 3 2 Ear Infection 3 1 Disturbance in Attention 3 1 Pruritis 3 0 Table 3 lists adverse reactions that occurred in at least 3% of adult patients with epilepsy treated with rufinamide tablets (up to 3200 mg per day) in adjunctive controlled studies and were numerically more common in patients treated with rufinamide tablets than in patients on placebo. In these studies, either rufinamide tablets or placebo was added to the current AED therapy. At all doses studied of up to 3200 mg per day given as adjunctive therapy in adults, the most common (≥ 3%) adverse reactions, and with the greatest increase in incidence compared to placebo, for rufinamide tablets were dizziness, fatigue, nausea, diplopia, vision blurred, and ataxia.

Table

3: Adverse Reactions in Adults in Pooled Double-Blind Adjunctive Trials Adverse Reaction Rufinamide Tablet (N=823)% Placebo (N=376)% Headache 27 26 Dizziness 19 12 Fatigue 16 10 Nausea 12 9 Somnolence 11 9 Diplopia 9 3 Tremor 6 5 Nystagmus 6 5 Blurred Vision 6 2 Vomiting 5 4 Ataxia 4 0 Upper Abdominal Pain 3 2 Anxiety 3 2 Constipation 3 2 Dyspepsia 3 2 Back Pain 3 1 Gait Disturbance 3 1 Vertigo 3 1 Discontinuation in Controlled Clinical Studies In controlled, double-blind, adjunctive clinical studies, 9% of pediatric and adult patients receiving rufinamide tablets as adjunctive therapy and 4% receiving placebo discontinued as a result of an adverse reaction. The adverse reactions most commonly leading to discontinuation of rufinamide tablet (>1%) used as adjunctive therapy were generally similar in adults and pediatric patients. In pediatric patients (ages 4 to less than 17 years) double-blind adjunctive clinical studies, 8% of patients receiving rufinamide tablets as adjunctive therapy (at the recommended dose of 45 mg/kg per day) and 2% receiving placebo discontinued as a result of an adverse reaction. The adverse reactions most commonly leading to discontinuation of rufinamide tablets (>1%) used as adjunctive therapy are presented in Table 4.

Table

4: Most Common Adverse Reactions Leading to Discontinuation in Pediatric Patients (Ages 4 to less than 17 years) in Pooled Double-Blind Adjunctive Trials Adverse Reaction Rufinamide Tablet (N=187)% Placebo(N=182)% Convulsion 2 1 Rash 2 1 Fatigue 2 0 Vomiting 1 0 In adult double-blind, adjunctive clinical studies, 10% of patients receiving rufinamide tablets as adjunctive therapy (at doses up to 3200 mg per day) and 6% receiving placebo discontinued as a result of an adverse reaction. The adverse reactions most commonly leading to discontinuation of rufinamide tablets (>1%) used as adjunctive therapy are presented in Table 5.

Table

5: Most Common Adverse Reactions Leading to Discontinuation in Adult Patients in Pooled Double-Blind Adjunctive Trials Adverse Reaction Rufinamide Tablet (N=823)% Placebo (N=376)% Dizziness 3 1 Fatigue 2 1 Headache 2 1 Nausea 1 0 Ataxia 1 0 Pediatric Patients ages 1 to less than 4 years In a multicenter, parallel group, open-label study comparing rufinamide tablets (45 mg/kg per day) adjunctive treatment (n=25) to the adjunctive treatment with an AED of the investigator’s choice (n=11) in pediatric patients (1 year to less than 4 years of age) with inadequately controlled Lennox-Gastaut Syndrome, the adverse reaction profile was generally similar to that observed in adults and pediatric patients 4 years of age and older treated with rufinamide tablets. Adverse reactions that occurred in at least 2 (8 %) rufinamide tablet-treated patients and with a higher frequency than in the AED comparator group were: vomiting (24%), somnolence (16%), bronchitis (12%), constipation (12%), cough (12%), decreased appetite (12%), rash (12%), otitis media (8%), pneumonia (8%), decreased weight (8%), gastroenteritis (8%), nasal congestion (8%), and pneumonia aspiration (8%).

Other Adverse Reactions Observed During

Clinical Trials Rufinamide tablet has been administered to 1978 individuals during all epilepsy clinical trials (placebo-controlled and open-label). Adverse reactions occurring during these studies were recorded by the investigators using terminology of their own choosing. To provide a meaningful estimate of the proportion of patients having adverse reactions, these events were grouped into standardized categories using the MedDRA dictionary. Adverse events occurring at least three times and considered possibly related to treatment are included in the System Organ Class listings below. Terms not included in the listings are those already included in the tables above, those too general to be informative, those related to procedures, and terms describing events common in the population. Some events occurring fewer than 3 times are also included based on their medical significance. Because the reports include events observed in open-label, uncontrolled observations, the role of rufinamide tablet in their causation cannot be reliably determined. Events are classified by body system and listed in order of decreasing frequency as follows: frequent adverse events— those occurring in at least 1/100 patients; infrequent adverse events— those occurring in 1/100 to 1/1000 patients; rare— those occurring in fewer than 1/1000 patients. Blood and Lymphatic System Disorders: Frequent : anemia. Infrequent : lymphadenopathy, leukopenia, neutropenia, iron deficiency anemia, thrombocytopenia.

Cardiac

Disorders: Infrequent: bundle branch block right, atrioventricular block first degree. Metabolic and Nutritional Disorders: Frequent: decreased appetite, increased appetite. Renal and Urinary Disorders: Frequent: pollakiuria. Infrequent: urinary incontinence, dysuria, hematuria, nephrolithiasis, polyuria, enuresis, nocturia, incontinence.

6.2 Postmarketing Experience The following adverse reactions have been identified during post approval use of rufinamide tablets. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Dermatologic: Stevens-Johnson syndrome and other serious skin rashes with mucosal involvement.

AND PRECAUTIONS Monitor patients for new or worsening depression, suicidal thoughts/behavior, and unusual changes in mood or behavior ( 5.1 ) Central nervous system reactions can occur ( 5.2 ) Use caution when administering rufinamide tablets with other drugs that shorten the QT interval ( 5.3 ) Discontinue rufinamide tablet if multi-organ hypersensitivity reaction occurs ( 5.4 ) Withdraw rufinamide tablet gradually to minimize the risk of precipitating seizures, seizure exacerbation, or status epilepticus ( 5.5 )

5.1 Suicidal Behavior and Ideation Antiepileptic drugs (AEDs), including rufinamide tablets, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and or any unusual changes in mood or behavior. Pooled analyses of 199 placebo-controlled clinical trials (mono-and adjunctive therapy) of 11 different AEDs showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI:1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. In these trials, which had a median treatment duration of 12 weeks, the estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in drug-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion about drug effect on suicide. The increased risk of suicidal thoughts or behavior with AEDs was observed as early as 1 week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed. The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed. The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age (5 to 100 years) in the clinical trials analyzed.

Table

1 shows absolute and relative risk by indication for all evaluated AEDs.

Table

1: Absolute and Relative Risk of Suicidal Behavior and Ideation Indication Placebo Patients with Events Per 1000 Patients Drug Patients with Events Per 1000 Patients Relative Risk: Incidence of Events in Drug Patients/Incidence in Placebo Patients Risk Difference: Additional Drug Patients with Events Per 1000 Patients Epilepsy 1 3.4 3.5

2.4 Psychiatric 5.7 8.5 1.5

2.9 Other 1 1.8 1.9

0.9 Total 2.4 4.3 1.8

1.9 The relative risk for suicidal thoughts or behavior was higher in clinical trials for epilepsy than in clinical trials for psychiatric or other conditions, but the absolute risk differences were similar for the epilepsy and psychiatric indications. Anyone considering prescribing rufinamide tablets or any other AED must balance the risk of suicidal thoughts or behavior with the risk of untreated illness. Epilepsy and many other illnesses for which AEDs are prescribed are themselves associated with morbidity and mortality and an increased risk of suicidal thoughts and behavior. Should suicidal thoughts and behavior emerge during treatment, consider whether the emergence of these symptoms in any given patient may be related to the illness being treated.

5.2 Central Nervous System Reactions Use of rufinamide tablets has been associated with central nervous system-related adverse reactions in the controlled clinical trial of patients 4 years or older with Lennox-Gastaut Syndrome. The most significant of these can be classified into two general categories: 1) somnolence or fatigue, and 2) coordination abnormalities, dizziness, gait disturbances, and ataxia. Somnolence was reported in 24% of rufinamide tablet-treated patients compared to 13% of patients on placebo, and led to study discontinuation in 3% of rufinamide tablet-treated patients compared to 0% of patients on placebo. Fatigue was reported in 10% of rufinamide tablet-treated patients compared to 8% of patients on placebo patients. It led to study discontinuation in 1% of rufinamide tablet-treated patients and 0% of patients on placebo patients. Dizziness was reported in 2.7% of rufinamide tablet-treated patients compared to 0% of patients on placebo, and did not lead to study discontinuation. Ataxia and gait disturbance were reported in 5.4% and 1.4% of rufinamide tablet-treated patients, respectively, compared to no patient on placebo. None of these reactions led to study discontinuation. Accordingly, patients should be advised not to drive or operate machinery until they have gained sufficient experience on rufinamide tablet to gauge whether it adversely affects their ability to drive or operate machinery.

5.3 QT Shortening Formal cardiac ECG studies demonstrated shortening of the QT interval (mean=20 msec, for doses &gt;2400 mg twice daily) with rufinamide tablets. In a placebo-controlled study of the QT interval, a higher percentage of rufinamide tablet-treated subjects (46% at 2400 mg, 46% at 3200 mg, and 65% at 4800 mg) had a QT shortening of greater than 20 msec at T max compared to placebo (5 to 10%). Reductions of the QT interval below 300 msec were not observed in the formal QT studies with doses up to 7200 mg per day. Moreover, there was no signal for drug-induced sudden death or ventricular arrhythmias. The degree of QT shortening induced by rufinamide tablets is without any known clinical risk.

Familial

Short QT syndrome is associated with an increased risk of sudden death and ventricular arrhythmias, particularly ventricular fibrillation. Such events in this syndrome are believed to occur primarily when the corrected QT interval falls below 300 msec. Non-clinical data also indicate that QT shortening is associated with ventricular fibrillation. Patients with Familial Short QT syndrome should not be treated with rufinamide tablets. Caution should be used when administering rufinamide tablet with other drugs that shorten the QT interval [see Contraindications (4) ] .

5.4 Multi-organ Hypersensitivity/Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)

Drug

Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as multi-organ hypersensitivity, has been reported in patients taking antiepileptic drugs, including rufinamide tablets. DRESS may be fatal or life-threatening. DRESS typically, although not exclusively, presents with fever, rash, and/or lymphadenopathy, and/or facial swelling, in association with other organ system involvement, such as hepatitis, nephritis, hematological abnormalities, myocarditis, or myositis, sometimes resembling an acute viral infection. Eosinophilia is often present. It is important to note that early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident. Because this disorder is variable in its expression, other organ systems not noted here may be involved. All cases of DRESS identified in clinical trials with rufinamide tablets occurred in pediatric patients less than 12 years of age, occurred within 4 weeks of treatment initiation, and resolved or improved with rufinamide tablet discontinuation. DRESS has also been reported in adult and pediatric patients taking rufinamide tablets in the postmarketing setting. If DRESS is suspected, the patient should be evaluated immediately, rufinamide tablets should be discontinued, and alternative treatment should be started.

5.5 Withdrawal of AEDs As with all antiepileptic drugs, rufinamide tablets should be withdrawn gradually to minimize the risk of precipitating seizures, seizure exacerbation, or status epilepticus. If abrupt discontinuation of the drug is medically necessary, the transition to another AED should be made under close medical supervision. In clinical trials, rufinamide tablets discontinuation was achieved by reducing the dose by approximately 25% every 2 days.

5.6 Status Epilepticus Estimates of the incidence of treatment emergent status epilepticus among patients treated with rufinamide tablets are difficult because standard definitions were not employed. In a controlled Lennox-Gastaut Syndrome trial, 3 of 74 (4.1%) rufinamide tablet-treated patients had episodes that could be described as status epilepticus in the rufinamide tablet-treated patients compared with none of the 64 patients in the placebo-treated patients. In all controlled trials that included patients with different epilepsies, 11 of 1240 (0.9%) rufinamide tablet-treated patients had episodes that could be described as status epilepticus compared with none of 635 patients in the placebo-treated patients.

5.7 Leukopenia Rufinamide tablet has been shown to reduce white cell count. Leukopenia (white cell count &lt; 3X10 9 L) was more commonly observed in rufinamide tablet-treated patients 43 of 1171 (3.7%) than placebo-treated patients, 7 of 579 (1.2%) in all controlled trials.

INTERACTIONS

• Patients on valproate should begin at a rufinamide dose lower than 10 mg/kg per day (pediatric patients) or 400 mg per day (adults) ( 7.2 )
• Hormonal contraceptives may be less effective with rufinamide; use additional non-hormonal forms of contraception ( 7.3 )

7.1 Effects of Rufinamide on other AEDs Population pharmacokinetic analysis of average concentration at steady state of carbamazepine, lamotrigine, phenobarbital, phenytoin, topiramate, and valproate showed that typical rufinamide C avss levels had little effect on the pharmacokinetics of other AEDs. Any effects, when they occur, have been more marked in the pediatric population.

Table

6 summarizes the drug-drug interactions of rufinamide with other AEDs.

Table

6: Summary of drug-drug interactions of rufinamide with other antiepileptic drugs AED Co- administered Influence of Rufinamide on AED concentration a) Influence of AED on Rufinamide concentration Carbamazepine Decrease by 7 to 13% b) Decrease by 19 to 26% Dependent on dose of carbamazepine Lamotrigine Decrease by 7 to 13% b)

No Effect Phenobarbital

Increase by 8 to 13% b) Decrease by 25 to 46% c), d) Independent of dose or concentration of phenobarbital Phenytoin Increase by 7 to 21% b) Decrease by 25 to 46% c),d) Independent of dose or concentration of phenytoin Topiramate No Effect No Effect Valproate No Effect Increase by <16 to 70% c) Dependent on concentration of valproate Primidone Not Investigated Decrease by 25 to 46% c), d) Independent of dose or concentration of primidone Benzodiazepines e)

Not Investigated No

Effect a) Predictions are based on rufinamide concentrations at the maximum recommended dose of rufinamide. b) Maximum changes predicted to be in pediatric patients and in adult patients who achieve significantly higher levels of rufinamide, as the effect of rufinamide on these AEDs is concentration-dependent. c) Larger effects in pediatric patients at high doses/concentrations of AEDs. d) Phenobarbital, primidone and phenytoin were treated as a single covariate (phenobarbital-type inducers) to examine the effect of these agents on rufinamide clearance. e) All compounds of the benzodiazepine class were pooled to examine for ‘class effect’ on rufinamide clearance. Phenytoin: The decrease in clearance of phenytoin estimated at typical levels of rufinamide (C avss 15 mcg/mL) is predicted to increase plasma levels of phenytoin by 7 to 21%. As phenytoin is known to have non-linear pharmacokinetics (clearance becomes saturated at higher doses), it is possible that exposure will be greater than the model prediction.

7.2 Effects of other AEDs on Rufinamide Potent cytochrome P450 enzyme inducers, such as carbamazepine, phenytoin, primidone, and phenobarbital, appear to increase the clearance of rufinamide (see Table 6). Given that the majority of clearance of rufinamide is via a non-CYP-dependent route, the observed decreases in blood levels seen with carbamazepine, phenytoin, phenobarbital, and primidone are unlikely to be entirely attributable to induction of a P450 enzyme. Other factors explaining this interaction are not understood. Any effects, where they occurred, were likely to be more marked in the pediatric population.

Valproate

Patients stabilized on rufinamide before being prescribed valproate should begin valproate therapy at a low dose, and titrate to a clinically effective dose. Similarly, patients on valproate should begin at a rufinamide dose lower than 10 mg/kg per day (pediatric patients) or 400 mg per day (adults) [ see Dosage and Administration (2.5 ), Clinical Pharmacology ( 12.3 )].

7.3 Effects of Rufinamide on Hormonal Contraceptives Female patients of childbearing age should be warned that the concurrent use of rufinamide with hormonal contraceptives may render this method of contraception less effective. Additional non-hormonal forms of contraception are recommended when using rufinamide [ see Use in Specific Populations ( 8.3 ), Clinical Pharmacology ( 12.3 ) and Patient Counseling Information ( 17 ) ].

Drug Interactions

Based on in vitro studies, rufinamide shows little or no inhibition of most cytochrome P450 enzymes at clinically relevant concentrations, with weak inhibition of CYP 2E1. Drugs that are substrates of CYP 2E1 (e.g., chlorzoxazone) may have increased plasma levels in the presence of rufinamide, but this has not been studied. Based on a population pharmacokinetic analysis, rufinamide clearance was decreased by valproate. In pediatric patients, valproate administration may lead to elevated levels of rufinamide by up to 70% [ see Drug Interactions ( 7.2 )] . Based on in vivo drug interaction studies with triazolam and oral contraceptives, rufinamide is a weak inducer of the CYP 3A4 enzyme and can decrease exposure of drugs that are substrates of CYP 3A4.

• Co-administration and pre-treatment of rufinamide (400 mg twice daily) and triazolam resulted in a 37% decrease in AUC and a 23% decrease in C max of triazolam, a CYP 3A4 substrate.
• Co-administration of rufinamide (800 mg twice daily for 14 days) and Ortho-Novum 1/35 ® resulted in a mean decrease in the ethinyl estradiol AUC 0 to 24 of 22% and C max by 31% and norethindrone AUC 0 to 24 by 14% and C max by 18%, respectively. The clinical significance of this decrease is unknown [see Drug Interactions ( 7.3 ) and Use in Specific Populations ( 8.3 )] . Rufinamide is metabolized by carboxylesterases. Drugs that may induce the activity of carboxylesterases may increase the clearance of rufinamide. Broad-spectrum inducers such as carbamazepine and phenobarbital may have minor effects on rufinamide metabolism via this mechanism. Drugs that are inhibitors of carboxylesterases may decrease metabolism of rufinamide.