Adults and Pediatric Patients 10 Years and Older with Partial Onset or Primary Generalized Tonic-Clonic Seizures

The recommended dose for topiramate monotherapy in adults and in pediatric patients 10 years of age and older is 400 mg orally once daily. Titrate TROKENDI XR® according to the following schedule:

Pediatric Patients Ages 6 to less than 10 Years

Dosing of topiramate as initial monotherapy in pediatric patients 6 to less than 10 years of age with partial onset or primary generalized tonic-clonic seizures was based on a pharmacometric bridging approach [see Clinical Studies (14.1)].

Dosing in patients 6 to less than 10 years is based on weight. During the titration period, the initial dose of TROKENDI XR® should be 25 mg/day administered nightly for the first week. Based upon tolerability, the dosage can be increased to 50 mg/day in the second week. Dosage can be increased by 25-50 mg/day each subsequent week as tolerated. Titration to the minimum maintenance dose should be attempted over 5-7 weeks of the total titration period. Based upon tolerability and clinical response, additional titration to a higher dose (up to the maximum maintenance dose) can be attempted at 25-50 mg/day weekly increments. The total daily dose should not exceed the maximum maintenance dose for each range of body weight (Table 1).

Adults 17 Years of Age and Over with Partial Onset Seizures, Primary Generalized Tonic-Clonic Seizures, or Lennox-Gastaut Syndrome

The recommended total daily dose of TROKENDI XR® as adjunctive therapy in adults with partial onset seizures or Lennox-Gastaut Syndrome is 200 mg to 400 mg orally once daily and with primary generalized tonic-clonic seizures is 400 mg orally once daily.

Initiate therapy at 25 mg to 50 mg once daily followed by titration to an effective dose in increments of 25 mg to 50 mg every week. Daily topiramate doses above 1600 mg have not been studied.

In the study of primary generalized tonic-clonic seizures using topiramate, the assigned dose was reached at the end of 8 weeks [see Clinical Studies (14.4)].

Pediatric Patients 6 to 16 Years of Age - Partial Onset Seizures, Primary Generalized Tonic-Clonic Seizures, or Lennox-Gastaut Syndrome

The recommended total daily dose of TROKENDI XR® as adjunctive therapy for pediatric patients with partial onset seizures, primary generalized tonic-clonic seizures, or seizures associated with Lennox-Gastaut syndrome is approximately 5 mg/kg to 9 mg/kg orally once daily. Begin titration at 25 mg once daily (based on a range of 1 mg/kg/day to 3 mg/kg/day) given nightly for the first week. Subsequently, increase the dosage at 1- or 2-week intervals by increments of 1 mg/kg to 3 mg/kg to achieve optimal clinical response. Dose titration should be guided by clinical outcome. If required, longer intervals between dose adjustments can be used.

In the study of primary generalized tonic-clonic seizures, the assigned dose of 6 mg/kg once daily was reached at the end of 8 weeks [see Clinical Studies (14.4)].

Manifestations of Metabolic Acidosis

Some manifestations of acute or chronic metabolic acidosis may include hyperventilation, nonspecific symptoms such as fatigue and anorexia, or more severe sequelae including cardiac arrhythmias or stupor. Chronic, untreated metabolic acidosis may increase the risk for nephrolithiasis or nephrocalcinosis, and may also result in osteomalacia (referred to as rickets in pediatric patients) and/or osteoporosis with an increased risk for fractures. Chronic metabolic acidosis in pediatric patients may also reduce growth rates. A reduction in growth rate may eventually decrease the maximal height achieved. The effect of topiramate on growth and bone-related sequelae has not been systematically investigated in long-term, placebo-controlled trials. Long-term, open-label treatment of infants/toddlers, with intractable partial epilepsy, for up to 1 year, showed reductions from baseline in Z SCORES for length, weight, and head circumference compared to age and sex-matched normative data, although these patients with epilepsy are likely to have different growth rates than normal infants. Reductions in Z SCORES for length and weight were correlated to the degree of acidosis [see Pediatric Use (8.4)]. Topiramate treatment that causes metabolic acidosis during pregnancy can possibly produce adverse effects on the fetus and might also cause metabolic acidosis in the neonate from possible transfer of topiramate to the fetus [see Warnings and Precautions (5.8) and Use in Specific Populations (8.1)].

Epilepsy

Migraine

Adult Patients

Pediatric Patients

Hyperammonemia/Encephalopathy Without Concomitant Valproic Acid (VPA)

Topiramate treatment has produced hyperammonemia (in some instances dose-related) in a clinical investigational program in adolescent patients (12 to 17 years) who were treated with topiramate for migraine prophylaxis. The incidence of hyperammonemia (above the upper limit of normal reference) at any time in the trial was 9% for placebo, 14% for 50 mg, and 26% for 100 mg topiramate daily. In some patients, hyperammonemia was observed at the end of the trial at the final visit. The incidence of markedly increased hyperammonemia (at least 50% or higher above upper limit of normal) at any time in the trial in adolescent patients was also increased at 100 mg/day (9%) compared to 50 mg topiramate (0%) or placebo (3%). During this trial, markedly increased ammonia levels returned to normal in all but one patient (in whom the ammonia level fell to high instead of markedly abnormal).

Topiramate treatment has produced hyperammonemia in a clinical investigational program in very young pediatric patients (1 month to 24 months) who were treated with adjunctive topiramate for partial onset epilepsy (8% for placebo, 10% for 5 mg/kg/day, 0% for 15 mg/kg/day, 9% for 25 mg/kg/day). TROKENDI XR® is not approved as adjunctive treatment of partial onset seizures in pediatric patients less than 6 years old. In some patients, ammonia was markedly increased (greater than or equal to 50% above upper limit of normal). The hyperammonemia associated with topiramate treatment occurred with and without encephalopathy in placebo-controlled trials, and in an open-label, extension trial of infants with refractory epilepsy. Dose-related hyperammonemia was also observed in the extension trial in pediatric patients up to 2 years old. Clinical symptoms of hyperammonemic encephalopathy often include acute alterations in level of consciousness and/or cognitive function with lethargy or vomiting.

Hyperammonemia with and without encephalopathy has also been observed in postmarketing reports in patients who were taking topiramate without concomitant valproic acid (VPA).

Hyperammonemia/Encephalopathy With Concomitant Valproic Acid (VPA)

Concomitant administration of topiramate and valproic acid (VPA) has been associated with hyperammonemia with or without encephalopathy in patients who have tolerated either drug alone based upon postmarketing reports. Although hyperammonemia may be asymptomatic, clinical symptoms of hyperammonemic encephalopathy often include acute alterations in level of consciousness and/or cognitive function with lethargy or vomiting. In most cases, symptoms and signs abated with discontinuation of either drug. This adverse reaction is not due to a pharmacokinetic interaction.

Although TROKENDI XR® is not indicated for use in infants/toddlers (1 month to 24 months), topiramate with concomitant VPA clearly produced a dose-related increase in the incidence of hyperammonemia (above the upper limit of normal, 0% for placebo, 12% for 5 mg/kg/day, 7% for 15 mg/kg/day, 17% for 25 mg/kg/day) in an investigational program using topiramate. Markedly increased, dose-related hyperammonemia (0% for placebo and 5 mg/kg/day, 7% for 15 mg/kg/day, and 8% for 25 mg/kg/day) also occurred in these infants/toddlers. Dose-related hyperammonemia was similarly observed in a long-term, extension trial utilizing topiramate in these very young, pediatric patients [see Use in Specific Populations (8.4)].

Hyperammonemia with and without encephalopathy has also been observed in postmarketing reports in patients taking topiramate with valproic acid (VPA).

The hyperammonemia associated with topiramate treatment appears to be more common when used concomitantly with VPA.

Monitoring for Hyperammonemia

Patients with inborn errors of metabolism or reduced hepatic mitochondrial activity may be at an increased risk for hyperammonemia with or without encephalopathy. Although not studied, topiramate or TROKENDI XR® treatment or an interaction of concomitant topiramate-based product and valproic acid treatment may exacerbate existing defects or unmask deficiencies in susceptible persons.

In patients who develop unexplained lethargy, vomiting, or changes in mental status associated with any topiramate treatment, hyperammonemic encephalopathy should be considered and an ammonia level should be measured.

Increased Risk for Bleeding

Topiramate treatment is associated with an increased risk for bleeding. In a pooled analysis of placebo-controlled studies of approved and unapproved indications, bleeding was more frequently reported as an adverse event for topiramate than for placebo (4.5% versus 3.0% in adult patients, and 4.4% versus 2.3% in pediatric patients). In this analysis, the incidence of serious bleeding events for topiramate and placebo was 0.3% versus 0.2% for adult patients, and 0.4% versus 0% for pediatric patients.

Adverse bleeding reactions reported with topiramate ranged from mild epistaxis, ecchymosis, and increased menstrual bleeding to life-threatening hemorrhages. In patients with serious bleeding events, conditions that increased the risk for bleeding were often present, or patients were often taking drugs that cause thrombocytopenia (other antiepileptic drugs) or affect platelet function or coagulation (e.g., aspirin, nonsteroidal anti-inflammatory drugs, selective serotonin reuptake inhibitors, or warfarin or other anticoagulants).

Clinical Trials Experience in Epilepsy

Clinical Trial Experience in Migraine

Laboratory Abnormalities

Topiramate decreases serum bicarbonate [see Warnings and Precautions (5.4)]

Topiramate treatment with or without concomitant valproic acid (VPA) can cause hyperammonemia with or without encephalopathy [see Warnings and Precautions (5.10)].

Immediate-release topiramate treatment was associated with changes in several clinical laboratory analytes in randomized, double-blind, placebo-controlled studies. Similar effects should be anticipated with use of TROKENDI XR®.

Pregnancy Exposure Registry

There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to topiramate during pregnancy. Patients should be encouraged to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry if they become pregnant. This registry is collecting information about the safety of antiepileptic drugs during pregnancy. To enroll, patients can call the toll-free number 1-888-233-2334. Information about the North American Drug Pregnancy Registry can be found at http://www.aedpregnancyregistry.org/.

Risk Summary

Topiramate can cause fetal harm when administered to a pregnant woman. Data from pregnancy registries indicate that infants exposed to topiramate in utero have increased risk for cleft lip and/or cleft palate (oral clefts) and for being small for gestational age [see Human Data].

In multiple animal species, topiramate demonstrated developmental toxicity, including teratogenicity, in the absence of maternal toxicity at clinically relevant doses [see Animal Data].

In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively.

Clinical Considerations

Data

Risk Summary

Topiramate is excreted in human milk [see Data]. The effects of topiramate exposure in breastfed infants are unknown.

The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for TROKENDI XR and any potential adverse effects on the breastfed infant from TROKENDI XR or from the underlying maternal condition.

Data

Limited data from 5 women with epilepsy treated with topiramate during lactation showed drug levels in milk similar to those in maternal plasma.

Contraception

Women of childbearing potential who are not planning a pregnancy should use effective contraception because of the risks to the fetus of oral clefts and of being small for gestational age [see Drug Interactions (7.2) and Use in Specific Populations (8.1)].

Seizures in Pediatric Patients 6 Years of Age and Older

The safety and effectiveness of TROKENDI XR® for treatment of partial onset seizures, primary generalized tonic-clonic seizures, or Lennox-Gastaut syndromes in pediatric patients at least 6 years of age is based on controlled trials with immediate-release topiramate [see Clinical Studies (14.2, 14.3, 14.4 and 14.5)].

The adverse reactions in pediatric patients treated for partial onset seizure, primary generalized tonic-clonic seizures, or Lennox-Gastaut syndrome are similar to those seen in adults [see Warnings and Precautions (5) and Adverse Reactions (6)].

These include, but are not limited to:

• oligohydrosis and hyperthermia [see Warnings and Precautions (5.3)]
• dose-related increased incidence of metabolic acidosis [see Warnings and Precautions (5.4)]
• dose-related increased incidence of hyperammonemia [see Warnings and Precautions (5.10)]

Not Recommended for Pediatric Patients Younger than 6 Years of Age

The safety and effectiveness of TROKENDI XR for treatment of partial onset seizures, primary generalized tonic-clonic seizures, or Lennox-Gastaut syndromes in pediatric patients younger than 6 years of age has not been established.

Because the capsule must be swallowed whole, and may not be sprinkled on food, crushed or chewed, TROKENDI XR® is recommended only for children age 6 or older.

The following pediatric use information for adjunctive treatment for partial onset epilepsy in infants and toddlers (1 to 24 months) is based on studies conducted with immediate-release topiramate, which failed to demonstrate efficacy.

Safety and effectiveness of immediate-release topiramate in patients below the age of 2 years have not been established for the adjunctive therapy treatment of partial onset seizures, primary generalized tonic-clonic seizures, or seizures associated with Lennox-Gastaut syndrome. In a single randomized, double-blind, placebo-controlled investigational trial, the efficacy, safety, and tolerability of immediate-release topiramate oral liquid and sprinkle formulations as an adjunct to concurrent antiepileptic drug therapy in infants 1 to 24 months of age with refractory partial onset seizures, was assessed. After 20 days of double-blind treatment, immediate-release topiramate (at fixed doses of 5 mg/kg, 15 mg/kg, and 25 mg/kg per day) did not demonstrate efficacy compared with placebo in controlling seizures.

In general, the adverse reaction profile in this population was similar to that of older pediatric patients, although results from the above controlled study, and an open-label, long-term extension study in these infants/toddlers (1 to 24 months old) suggested some adverse reactions not previously observed in older pediatric patients and adults; i.e., growth/length retardation, certain clinical laboratory abnormalities, and other adverse reactions that occurred with a greater frequency and/or greater severity than had been recognized previously from studies in older pediatric patients or adults for various indications.

These very young pediatric patients appeared to experience an increased risk for infections (any topiramate dose 12%, placebo 0%) and of respiratory disorders (any topiramate dose 40%, placebo 16%). The following adverse reactions were observed in at least 3% of patients on immediate-release topiramate and were 3% to 7% more frequent than in patients on placebo: viral infection, bronchitis, pharyngitis, rhinitis, otitis media, upper respiratory infection, cough, and bronchospasm. A generally similar profile was observed in older children [see Adverse Reactions (6)].

Immediate-release topiramate resulted in an increased incidence of patients with increased creatinine (any topiramate dose 5%, placebo 0%), BUN (any topiramate dose 3%, placebo 0%), and protein (any topiramate dose 34%, placebo 6%), and an increased incidence of decreased potassium (any topiramate dose 7%, placebo 0%). This increased frequency of abnormal values was not dose related. Creatinine was the only analyte showing a noteworthy increased incidence (topiramate 25 mg/kg/day 5%, placebo 0%) of a markedly abnormal increase [see Adverse Reactions (6.1)]. The significance of these findings is uncertain.

Immediate-release topiramate treatment also produced a dose-related increase in the percentage of patients who had a shift from normal at baseline to high/increased (above the normal reference range) in total eosinophil count at the end of treatment. The incidence of these abnormal shifts was 6 % for placebo, 10% for 5 mg/kg/day, 9% for 15 mg/kg/day, 14% for 25 mg/kg/day, and 11% for any topiramate dose [see Adverse Reactions (6.1)]. There was a mean dose-related increase in alkaline phosphatase. The significance of these findings is uncertain.

Topiramate produced a dose-related increased incidence of hyperammonemia [see Warnings and Precautions (5.10)].

Treatment with immediate-release topiramate for up to 1 year was associated with reductions in Z SCORES for length, weight, and head circumference [see Warnings and Precautions (5.4) and Adverse Reactions (6)].

In open-label, uncontrolled experience, increasing impairment of adaptive behavior was documented in behavioral testing over time in this population. There was a suggestion that this effect was dose-related. However, because of the absence of an appropriate control group, it is not known if this decrement in function was treatment related or reflects the patient's underlying disease (e.g., patients who received higher doses may have more severe underlying disease) [see Warnings and Precautions (5.7)].

In this open-label, uncontrolled study, the mortality was 37 deaths/1000 patient years. It is not possible to know whether this mortality rate is related to immediate-release topiramate treatment, because the background mortality rate for a similar, significantly refractory, young pediatric population (1 month to 24 months) with partial epilepsy is not known.

Other Pediatric Studies

Topiramate treatment produced a dose-related increased shift in serum creatinine from normal at baseline to an increased value at the end of 4 months treatment in adolescent patients (ages 12 years to 16 years) in a double-blind, placebo-controlled study [see Adverse Reactions (6.1)].

Migraine Prophylaxis in Adolescents 12 to 17 Years

Safety and effectiveness of topiramate in the prophylaxis of migraine was studied in 5 double-blind, randomized, placebo-controlled, parallel-group trials in a total of 219 pediatric patients, at doses of 50 mg/day to 200 mg/day, or 2 to 3 mg/kg/day. These comprised a fixed dose study in 103 adolescents age 12 to 17 years [see Clinical Studies (14.6)], a flexible dose (2 to 3 mg/kg/day), placebo-controlled study in 157 pediatric patients age 6 to 16 years (including 67 adolescent patients age 12 to 16 years), and a total of 49 adolescents age 12 to 17 years in 3 studies of migraine prophylaxis primarily in adults. Open-label extension phases of 3 studies enabled evaluation of long-term safety for up to 6 months after the end of the double-blind phase.

Efficacy of topiramate for migraine prophylaxis in adolescents is demonstrated for a 100 mg daily dose in Study 3 [see Clinical Studies (14.6)]. Efficacy of topiramate (2 to 3 mg/kg/day) for migraine prophylaxis was not demonstrated in a placebo-controlled trial of 157 pediatric patients (6 to 16 years) that included treatment of 67 adolescents (12 to 16 years) for 20 weeks.

In the adolescent trials (12 to 17 years) in which patients were randomized to placebo or a fixed daily dose of immediate-release topiramate, the most commonly observed adverse reactions associated with the use of immediate-release topiramate that were seen at an incidence higher (≥5%) than in the placebo group were: paresthesia, upper respiratory tract infection, anorexia, and abdominal pain [see Adverse Reactions (6.1)].

The most common cognitive adverse reaction in pooled double-blind studies in adolescent patients age 12 to 17 years was difficulty with concentration/attention [see Warnings and Precautions (5.7)].

Markedly abnormally low serum bicarbonate values indicative of metabolic acidosis were reported in topiramate-treated adolescent migraine patients [see Warnings and Precautions (5.4)].

In topiramate-treated adolescent patients (12 to 17 years) compared to placebo-treated patients, abnormally increased results were more frequent for creatinine, BUN, uric acid, chloride, ammonia, total protein, and platelets. Abnormally decreased results were observed with topiramate vs placebo treatment for phosphorus and bicarbonate [see Warnings and Precautions(5.4 and Adverse Reactions (6.1))].

Notable changes (increases and decreases) from baseline in systolic blood pressure, diastolic blood pressure, and pulse that were observed occurred more commonly in adolescents treated with topiramate compared to adolescents treated with placebo [see Clinical Pharmacology (12.2)].

Migraine Prophylaxis in Children 6-11 Years Old

Safety and effectiveness in pediatric patients below the age of 12 years have not been established for the prophylaxis treatment of migraine headache.

In a double-blind study in 90 children age 6 to 11 years (including 59 topiramate-treated and 31 placebo patients), the adverse reaction profile was generally similar to that in pooled double-blind studies of adolescents age 12 to 17 years. The adverse reactions that occurred most commonly in immediate-release topiramate-treated children age 6 to 11 years, and at least twice as frequently than placebo, were gastroenteritis (12% topiramate, 6% placebo), sinusitis (10% topiramate, 3% placebo), weight decrease (8% topiramate, 3% placebo) and paresthesia (7% topiramate, 0% placebo). Difficulty with concentration/attention occurred in 3 topiramate-treated patients (5%) and 0 placebo patients.

The risk for cognitive adverse reactions was greater in younger patients (6 to 11 years) than in older patients (12 to 17 years) [see Warnings and Precautions (5.7)].

For patients 6 to 11 years, the following were noted to be abnormally increased more frequently with topiramate than with placebo: alkaline phosphatase, creatinine, and eosinophils. Analytes abnormally decreased were: total white count and neutrophils [see Adverse Reactions (6.1)].

Serum bicarbonate, chloride, phosphorus, and ammonia data were not collected for pediatric patients 6 to 11 years of age.

Juvenile Animal Studies

When topiramate (30, 90, and 300 mg/kg/day) was administered orally to rats during the juvenile period of development (postnatal days 12 to 50), bone growth plate thickness was reduced in males at the highest dose tested. The higher of the doses not associated with effects on bone (90 mg/kg/day) is approximately 2 times the maximum recommended pediatric dose for epilepsy (9 mg/kg/day) on a body surface area (mg/m2) basis.

Absorption and Distribution

Linear pharmacokinetics of topiramate from TROKENDI XR® were observed following a single oral dose over the range of 50 mg to 200 mg. At 25 mg, the pharmacokinetics of TROKENDI XR® is nonlinear possibly due to the binding of topiramate to carbonic anhydrase in red blood cells.

The peak plasma concentrations (Cmax) of topiramate occurred at approximately 24 hours following a single 200 mg oral dose of TROKENDI XR®. At steady-state, the (AUC0-24, Cmax, and Cmin) of topiramate from TROKENDI XR® administered once-daily and the immediate-release tablet administered twice-daily were shown to be bioequivalent. Fluctuation of topiramate plasma concentrations at steady-state for TROKENDI XR® administered once-daily was approximately 26% and 42% in healthy subjects and in epileptic patients, respectively, compared to approximately 40% and 51%, respectively, for immediate-release topiramate [see Clinical Pharmacology (12.6)].

Compared to the fasted state, high-fat meal increased the Cmax of topiramate by 37% and shortened the Tmax to approximately 8 hour following a single dose of TROKENDI XR®, while having no effect on the AUC. Modeling of the observed single dose fed data with simulation to steady state showed that the effect on Cmax is significantly reduced following repeat administrations. TROKENDI XR® can be taken without regard to meals.

Topiramate is 15% to 41% bound to human plasma proteins over the blood concentration range of 0.5 mcg/mL to 250 mcg/mL. The fraction bound decreased as blood concentration increased.

Carbamazepine and phenytoin do not alter the binding of immediate-release topiramate. Sodium valproate, at 500 mcg/mL (a concentration 5 to 10 times higher than considered therapeutic for valproate) decreased the protein binding of immediate-release topiramate from 23% to 13%. Immediate-release topiramate does not influence the binding of sodium valproate.

Metabolism and Excretion

Topiramate is not extensively metabolized and is primarily eliminated unchanged in the urine (approximately 70% of an administered dose). Six metabolites have been identified in humans, none of which constitutes more than 5% of an administered dose. The metabolites are formed via hydroxylation, hydrolysis, and glucuronidation. There is evidence of renal tubular reabsorption of topiramate. In rats, given probenecid to inhibit tubular reabsorption, along with topiramate, a significant increase in renal clearance of topiramate was observed. This interaction has not been evaluated in humans. Overall, oral plasma clearance (CL/F) is approximately 20 mL/min to 30 mL/min in adults following oral administration. The mean elimination half-life of topiramate was approximately 31 hours following repeat administration of TROKENDI XR®.

Specific Populations

Drug-Drug Interaction Studies

Drug/Laboratory Tests Interactions

There are no known interactions of TROKENDI XR® with commonly used laboratory tests.

Study in Healthy Normal Volunteers

TROKENDI XR® taken once a day provides steady state plasma levels comparable to immediate-release topiramate taken every 12 hours, when administered at the same total 200-mg daily dose. In a crossover study, 33 healthy subjects were titrated to a 200-mg dose of either TROKENDI XR® or immediate-release topiramate and were maintained at 200 mg per day for 10 days.

The 90% CI for the ratios of AUC0-24, Cmax and Cmin, as well as partial AUC (the area under the concentration-time curve from time 0 to time p (post dose) for multiple time points were within the 80 to 125% bioequivalence limits, indicating no clinically significant difference between the two formulations. In addition, the 90% CI for the ratios of topiramate plasma concentration at each of multiple time points over 24 hours for the two formulations were within the 80 to 125% bioequivalence limits, except for the initial time points before 1.5 hour post-dose.

Study in Patients with Epilepsy

In a study in epilepsy patients treated with immediate-release topiramate alone or in combination with either enzyme-inducing or neutral AEDs who were switched to an equivalent daily dose of TROKENDI XR®, there was a 10% decrease in AUC0-24, Cmax, and Cmin on the first day after the switch in all patients. At steady state, AUC0-24 and Cmax were comparable to immediate-release topiramate in all patients. While patients treated with TROKENDI XR® alone or in combination with neutral AEDs showed comparable Cmin at steady state, patients treated with enzyme-inducers showed a 10% decrease in Cmin. This difference is likely not clinically significant and probably due to the small number of patients on enzyme-inducers.

Carcinogenesis

An increase in urinary bladder tumors was observed in mice given topiramate (20, 75, and 300 mg/kg/day) in the diet for 21 months. An increase in the incidence of bladder tumors in males and females receiving 300 mg/kg was primarily due to the increased occurrence of a smooth muscle tumor considered histomorphologically unique to mice. The higher of the doses not associated with an increase in tumors (75 mg/kg/day) is equivalent to the maximum recommended human dose (MRHD) for epilepsy and approximately 4 times the MRHD for migraine (100 mg) on a mg/m2 basis. The relevance of this finding to human carcinogenic risk is uncertain.

No evidence of carcinogenicity was seen in rats following oral administration of topiramate for 2 years at doses up to 120 mg/kg/day (approximately 3 times the MRHD for epilepsy and 12 times the MRHD for migraine on a mg/m2 basis).

Mutagenesis

Topiramate did not demonstrate genotoxic potential when tested in a battery of in vitro and in vivo assays. Topiramate was not mutagenic in the Ames test or the in vitro mouse lymphoma assay; it did not increase unscheduled DNA synthesis in rat hepatocytes in vitro; and it did not increase chromosomal aberrations in human lymphocytes in vitro or in rat bone marrow in vivo.

Impairment of Fertility

No adverse effects on male or female fertility were observed in rats administered oral doses of up to 100 mg/kg/day (2.5 times the MRHD for epilepsy and 10 times the MRHD for migraine on a mg/m2 basis) prior to and during mating and early pregnancy.

Adults and Pediatric Patients 10 Years of Age and Older

The effectiveness of topiramate as initial monotherapy in adults and children 10 years of age and older with partial onset or primary generalized tonic-clonic seizures was established in a multicenter, randomized, double-blind, dose-controlled, parallel-group trial (Study 1).

Study 1 was conducted in 487 patients diagnosed with epilepsy (6 to 83 years of age) who had 1 or 2 well-documented seizures during the 3-month retrospective baseline phase who then entered the study and received topiramate 25 mg per day for 7 days in an open-label fashion. Forty-nine percent of subjects had no prior AED treatment and 17% had a diagnosis of epilepsy for greater than 24 months. Any AED therapy used for temporary or emergency purposes was discontinued prior to randomization. In the double-blind phase, 470 patients were randomized to titrate up to 50 mg per day or 400 mg per day of topiramate. If the target dose could not be achieved, patients were maintained on the maximum tolerated dose. Fifty-eight percent of patients achieved the maximal dose of 400 mg per day for greater than 2 weeks, and patients who did not tolerate 150 mg per day were discontinued.

The primary efficacy assessment was a between-group comparison of time to first seizure during the double-blind phase. Comparison of the Kaplan-Meier survival curves of time to first seizure favored the topiramate 400 mg per day group over the topiramate 50 mg per day group (p=0.0002, log rank test; Figure 1). The treatment effects with respect to time to first seizure were consistent across various patient subgroups defined by age, sex, geographic region, baseline body weight, baseline seizure type, time since diagnosis, and baseline AED use.

Figure 1: Kaplan-Meier Estimates of Cumulative Rates for Time to First Seizure in Study 1

Pediatric Patients 6 to Less than 10 Years of Age

The conclusion that topiramate is effective as initial monotherapy in pediatric patients 6 to less than 10 years of age with partial onset or primary generalized tonic-clonic seizures was based on a pharmacometric bridging approach using data from the controlled epilepsy trials conducted with immediate-release topiramate described in labeling. The approach consisted of first showing a similar exposure response relationship between pediatric patients down to 2 years of age and adults when immediate-release topiramate was given as adjunctive therapy [see Use in Specific Populations (8.4)]. Similarity of exposure-response was demonstrated in pediatric patients ages 6 to less than 16 years of age and adults when topiramate was given as initial monotherapy. Specific dosing in pediatric patients 6 to less than 10 years of age was derived from simulations utilizing plasma exposure ranges observed in pediatric and adult patients treated with immediate-release topiramate initial monotherapy[see Dosage and Administration (2.1)] .

Adult Patients with Partial Onset Seizures

The effectiveness of topiramate as an adjunctive treatment for adults with partial onset seizures was established in six multicenter, randomized, double-blind, placebo-controlled trials (Studies 2, 3, 4, 5, 6, and 7), two comparing several dosages of topiramate and placebo and four comparing a single dosage with placebo, in patients with a history of partial onset seizures, with or without secondarily generalized seizures.

Patients in these studies were permitted a maximum of two antiepileptic drugs (AEDs) in addition to topiramate tablets or placebo. In each study, patients were stabilized on optimum dosages of their concomitant AEDs during baseline phase lasting between 4 and 12 weeks. Patients who experienced a prespecified minimum number of partial onset seizures, with or without secondary generalization, during the baseline phase (12 seizures for 12-week baseline, 8 for 8-week baseline or 3 for 4-week baseline) were randomly assigned to placebo or a specified dose of topiramate tablets in addition to their other AEDs.

Following randomization, patients began the double-blind phase of treatment. In five of the six studies, patients received active drug beginning at 100 mg per day; the dose was then increased by 100 mg or 200 mg per day increments weekly or every other week until the assigned dose was reached, unless intolerance prevented increases. In Study 7, the 25 or 50 mg per day initial doses of topiramate were followed by respective weekly increments of 25 or 50 mg per day until the target dose of 200 mg per day was reached. After titration, patients entered a 4, 8 or 12-week stabilization period. The numbers of patients randomized to each dose, and the actual mean and median doses in the stabilization period are shown in Table 13.

Pediatric Patients Ages 2 to 16 Years with Partial Onset Seizures

The effectiveness of topiramate as an adjunctive treatment for pediatric patients ages 2 to 16 years with partial onset seizures was established in a multicenter, randomized, double-blind, placebo-controlled trial (Study 8), comparing topiramate and placebo in patients with a history of partial onset seizures, with or without secondarily generalized seizures.

Patients in Study 8 were permitted a maximum of two antiepileptic drugs (AEDs) in addition to topiramate tablets or placebo. In Study 8, patients were stabilized on optimum dosages of their concomitant AEDs during an 8-week baseline phase. Patients who experienced at least six partial onset seizures, with or without secondarily generalized seizures, during the baseline phase were randomly assigned to placebo or topiramate in addition to their other AEDs.

Following randomization, patients began the double-blind phase of treatment. Patients received active drug beginning at 25 or 50 mg per day; the dose was then increased by 25 mg to 150 mg per day increments every other week until the assigned dosage of 125, 175, 225 or 400 mg per day based on patients' weight to approximate a dosage of 6 mg/kg/day per day was reached, unless intolerance prevented increases. After titration, patients entered an 8-week stabilization period.

Adult Patients

The results of 2 multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trials conducted in US (Study 1) or the US and Canada (Study 2) established the effectiveness of immediate-release topiramate in the prophylactic treatment of migraine headache. The design of both trials was identical, enrolling patients with a history of migraine with or without aura, for at least 6 months, according to the International Headache Society (IHS) diagnostic criteria. Patients with a history of cluster headaches or basilar, opthalmoplegic, hemiplegic, or transformed migraine headaches were excluded from the trials. Patients were required to have completed up to a 2-week washout of any prior migraine preventative medications before starting the baseline phase.

Patients who experienced 3 to 12 migraine headaches over the 4 weeks in the baseline phase were randomized to either immediate-release topiramate 50 mg per day, 100 mg per day, 200 mg per day (twice the recommended daily dosage for migraine prophylaxis) or placebo, and treated for a total of 26 weeks (8-week titration period and 18-week maintenance period.). Treatment was initiated at 25 mg per day for one week, and then the daily dosage was increased by 25 mg increments each week until reaching the assigned target dose or maximum tolerated dose (administered twice daily).

Effectiveness of treatment was assessed by the reduction in migraine headache frequency, as measured by the change in 4-week migraine rate (according to migraines classified by IHS criteria) from the baseline phase to double-blind treatment period in each immediate-release topiramate treatment group compared to placebo in the Intent-To-Treat (ITT) population.

In Study 1, a total of 469 patients (416 females, 53 males) ranging in age from 13 to 70 years, were randomized and provided efficacy data. Two hundred sixty-five patients completed the entire 26-week double-blind phase. The median average daily dosages were 48 mg per day, 88 mg per day, and 132 mg per day in the target dose groups of topiramate 50, 100 and 200 mg per day, respectively.

The mean migraine headache frequency rate at baseline was approximately 5.5 migraine headaches per 28 days, and was similar across treatment groups. The change in the mean 4-week migraine headache frequency from baseline to the double-blind phase was -1.3, -2.1, and -2.2 in the immediate-release topiramate 50, 100, and 200 mg per day groups, respectively, versus -0.8 in the placebo group (see Figure 2). The treatment differences between the immediate release topiramate 100 and 200 mg per day groups versus placebo were similar and statistically significant (p less than 0.001 for both comparisons).

In Study 2, a total of 468 patients (406 females, 62 males) ranging in age from 12 to 65 years, were randomized and provided efficacy data. Two hundred fifty-five patients completed the entire 26-week double-blind phase. The median average daily dosages were 47 mg per day, 86 mg per day, and 150 mg per day in the target dose groups of immediate-release topiramate 50, 100, and 200 mg per day, respectively.

The mean migraine headache frequency rate at baseline was approximately 5.5 migraine headaches per 28 days and was similar across treatment groups. The change in the mean 4-week migraine headache period frequency from baseline to the double-blind phase was -1.4, -2.1, and -2.4 in the immediate-release topiramate 50, 100, and 200 mg per day groups, respectively, versus -1.1 in the placebo group (see Figure 2). The differences between the immediate-release topiramate 100 and 200 mg per day groups versus placebo were similar and statistically significant (p equals 0.008 and p less than 0.001, respectively).

In both studies there were no apparent differences in treatment effect within age or gender subgroups. Because most patients were Caucasian, there were insufficient numbers of patients from different races to make a meaningful comparison of race.

For patients withdrawing from immediate-release topiramate, daily dosages were decreased in weekly intervals by 25 to 50 mg per day.

Adolescent Patients Age 12 to 17 Years

The effectiveness of immediate-release topiramate as prophylaxis for migraine headache in adolescents was established in a multicenter, randomized, double-blind, parallel-group trial (Study 3). The study enrolled 103 patients (40 male, 63 female) age 12 to 17 years with episodic migraine headaches with or without aura. Patient selection was based on IHS criteria for migraines (using proposed revisions to the 1988 IHS pediatric migraine criteria [IHS-R criteria]).

Patients who experienced 3 to 12 migraine attacks (according to migraines classified by patient reported diaries) and ≤14 headache days (migraine and non-migraine) during the 4-week prospective baseline period were randomized to either immediate-release topiramate 50 mg/day, 100 mg/day, or placebo and treated for a total of 16 weeks (4-week titration period followed by a 12 week maintenance period). Treatment was initiated at 25 mg/day for one week, and then the daily dosage was increased by 25 mg increments each week until reaching the assigned target dose or maximum tolerated dose (administered twice daily). Approximately 80% or more patients in each treatment group completed the study. The median average daily dosages were 45 and 79 mg/day in the target dose groups of immediate-release topiramate 50 and 100 mg/day, respectively.

Effectiveness of treatment was assessed by comparing each immediate-release topiramate treatment group to placebo (ITT population) for the percent reduction from baseline to the last 12 weeks of the double-blind phase in the monthly migraine attack rate (primary endpoint). The percent reduction from baseline to the last 12 weeks of the double-blind phase in average monthly migraine attack rate is shown in Table 15. The 100 mg immediate-release topiramate dose produced a statistically significant treatment difference relative to placebo of 28% reduction from baseline in the monthly migraine attack rate.

The mean reduction from baseline to the last 12 weeks of the double-blind phase in average monthly attack rate, a key secondary efficacy endpoint in Study 3 (and the primary efficacy endpoint in Studies 1 and 2, of adults) was 3.0 for 100 mg immediate-release topiramate dose and 1.7 for placebo. This 1.3 treatment difference in mean reduction from baseline of montly migraine rate was statistically significant (p=0.0087).

Bottles

25 mg (light green opaque body/yellow opaque cap) topiramate extended-release capsules (black print "SPN" and "25") – bottles of 30 count (NDC-17772-101-30) and 100 count (NDC-17772-101-01)

50 mg (light green opaque body/orange opaque cap) topiramate extended-release capsules (black print "SPN" and "50") – bottles of 30 count (NDC-17772-102-30) and 100 count (NDC-17772-102-01)

100 mg (green opaque body/blue opaque cap) topiramate extended-release capsules (black print "SPN" and "100") – bottles of 30 count (NDC-17772-103-30) and 100 count (NDC-17772-103-01)

200 mg (pink opaque body/blue opaque cap) topiramate extended-release capsules (black print "SPN" and "200") – bottles of 30 count (NDC-17772-104-30) and 100 count (NDC-17772-104-01)

Blister package

25 mg (light green opaque body/yellow opaque cap) topiramate extended-release capsules (black print "SPN" and "25") – blister packages of 30-count (NDC-17772-101-15)

50 mg (light green opaque body/orange opaque cap) topiramate extended-release capsules (black print "SPN" and "50") – blister packages of 30-count (NDC-17772-102-15)

100 mg (green opaque body/blue opaque cap) topiramate extended-release capsules (black print "SPN" and "100") – blister packages of 30-count (NDC-17772-103-15)

200 mg (pink opaque body/blue opaque cap) topiramate extended-release capsules (black print "SPN" and "200") – blister packages of 30-count (NDC-17772-104-15)