Topamax Drug Information

Monotherapy Epilepsy TOPAMAX is indicated as initial monotherapy for the treatment of partial-onset or primary generalized tonic-clonic seizures in patients 2 years of age and older.

Adjunctive Therapy Epilepsy TOPAMAX is indicated as adjunctive therapy for the treatment of partial-onset seizures, primary generalized tonic-clonic seizures, and seizures associated with Lennox-Gastaut syndrome in patients 2 years of age and older.

Migraine TOPAMAX is indicated for the preventive treatment of migraine in patients 12 years of age and older.

Dosing in Monotherapy Epilepsy Adults and Pediatric Patients 10 Years of Age and Older The recommended dose for TOPAMAX monotherapy in adults and pediatric patients 10 years of age and older is 400 mg/day in two divided doses. During the titration period, the initial dose of TOPAMAX is 25 mg/day nightly for the first week. Based upon tolerability, the dosage can be increased to 50 mg/day (25 mg twice daily) 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 2). Table 2: Monotherapy Target Total Daily Maintenance Dosing for Patients 2 to 9 Years of Age

Dosing in Adjunctive Therapy Epilepsy Adults (17 Years of Age and Older) The recommended total daily dose of TOPAMAX as adjunctive therapy in adults with partial onset seizures or Lennox-Gastaut Syndrome is 200 to 400 mg/day in two divided doses, and 400 mg/day in two divided doses as adjunctive treatment in adults with primary generalized tonic-clonic seizures. Titrating in increments of 25 mg/day every week may delay the time to reach an effective dose. Doses above 400 mg/day have not been shown to improve responses in adults with partial-onset seizures.

Titration should begin at 25 mg/day (or less, based on a range of 1 to 3 mg/kg/day) nightly for the first week. The dosage should then be increased at 1- or 2-week intervals by increments of 1 to 3 mg/kg/day (administered in two divided doses), to achieve optimal clinical response. Dose titration should be guided by clinical outcome.

The total daily dose should not exceed 400 mg/day.

Dosing for the Preventive Treatment of Migraine

The recommended total daily dose of TOPAMAX as treatment for patients 12 years of age and older for the preventive treatment of migraine is 100 mg/day administered in two divided doses (Table 3). If required, longer intervals between dose adjustments can be used.

Administration Information TOPAMAX can be taken without regard to meals. TOPAMAX Tablets Because of the bitter taste, tablets should not be broken. TOPAMAX Sprinkle Capsules TOPAMAX Sprinkle Capsules may be swallowed whole or may be administered by carefully opening the capsule and sprinkling the entire contents on a small amount (teaspoon) of soft food.

This drug/food mixture should be swallowed immediately and not chewed. It should not be stored for future use.

Dosing in Patients with Renal Impairment

In patients with renal impairment (creatinine clearance less than 70 mL/min/1.73 m 2 ), one-half of the usual adult dose of TOPAMAX is recommended.

Dosing in Patients Undergoing Hemodialysis

To avoid rapid drops in topiramate plasma concentration during hemodialysis, a supplemental dose of TOPAMAX may be required. The actual adjustment should take into account 1 the duration of dialysis period, 2 the clearance rate of the dialysis system being used, and 3 the effective renal clearance of topiramate in the patient being dialyzed.

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, the incidence of adverse reactions observed in the clinical trials of a drug cannot be directly compared to the incidence of adverse reactions in the clinical trials of another drug, and may not reflect the incidence of adverse reactions observed in practice. Monotherapy Epilepsy Adults 16 Years of Age and Older The most common adverse reactions in the controlled clinical trial (Study 1) that occurred in adults in the 400 mg/day TOPAMAX group and at an incidence higher (≥ 10%) than in the 50 mg/day group were: paresthesia, weight loss and anorexia (see Table 5 ). The most common (≥ 2% more frequent than low-dose 50 mg/day TOPAMAX) adverse reactions causing discontinuation were difficulty with memory, fatigue, asthenia, insomnia, somnolence, and paresthesia.

Approximately 14% of the 77 pediatric patients in the 400 mg/day group who received TOPAMAX as monotherapy in the controlled clinical trial discontinued therapy due to adverse reactions. The most common (≥2% more frequent than low-dose 50 mg/day TOPAMAX) adverse reactions resulting in discontinuation were difficulty with concentration/attention, fever, flushing, and confusion. Table 5: Adverse Reactions in the High Dose Group As Compared to the Low Dose Group, in Monotherapy Epilepsy Trial (Study 1) in Adult and Pediatric Patients Years of Age and Older In pooled controlled clinical trials in adults with partial-onset seizures, primary generalized tonic-clonic seizures, or Lennox-Gastaut syndrome, 183 patients received adjunctive therapy with TOPAMAX at dosages of 200 to 400 mg/day (recommended dosage range) and 291 patients received placebo.

Patients in these trials were receiving 1 to 2 concomitant antiepileptic drugs in addition to TOPAMAX or placebo. The most common adverse reactions in the controlled clinical trial that occurred in adult patients in the 200–400 mg/day TOPAMAX group with an incidence higher (≥ 10%) than in the placebo group were: dizziness, speech disorders/related speech problems, somnolence, nervousness, psychomotor slowing, and vision abnormal (Table 6). The incidence of some adverse reactions (e.g., fatigue, dizziness, paresthesia, language problems, psychomotor slowing, depression, difficulty with concentration/attention, mood problems) was dose-related and much greater at higher than recommended TOPAMAX dosing (i.e., 600 mg – 1000 mg daily) compared to the incidence of these adverse reactions at the recommended dosing (200 mg to 400 mg daily) range.

In controlled clinical trials in adults, 11% of patients receiving TOPAMAX 200 to 400 mg/day as adjunctive therapy discontinued due to adverse reactions. This rate appeared to increase at dosages above 400 mg/day. Adverse reactions associated with discontinuing TOPAMAX included somnolence, dizziness, anxiety, difficulty with concentration or attention, fatigue and paresthesia.

The most common adverse reactions in the controlled clinical trial that occurred in pediatric patients in the 5 mg to 9 mg/kg/day TOPAMAX group with an incidence higher (≥ 10%) than in the placebo group were: fatigue and somnolence (Table 7). Patients may have reported more than one adverse reaction during the study and can be included in more than one adverse reaction category. 2 4 None of the pediatric patients who received TOPAMAX adjunctive therapy at 5 to 9 mg/kg/day in controlled clinical trials discontinued due to adverse reactions. Migraine Adults In the four multicenter, randomized, double-blind, placebo-controlled, parallel group migraine clinical trials for the preventive treatment of migraine (which included 35 pediatric patients 12 to 15 years of age), most adverse reactions occurred more frequently during the titration period than during the maintenance period.

The most common adverse reactions with TOPAMAX 100 mg in the clinical trials for the preventive treatment of migraine of predominantly adults that were seen at an incidence higher (≥ 5%) than in the placebo group were: paresthesia, anorexia, weight loss, taste perversion, diarrhea, difficulty with memory, hypoesthesia, and nausea (see Table 8 ). Table 8 includes those adverse reactions that occurred in the placebo-controlled trials where the incidence in any TOPAMAX treatment group was at least 3% and was greater than that for placebo patients. Patients may have reported more than one adverse reaction during the study and can be included in more than one adverse reaction category. patients exposed to TOPAMAX in the adult placebo-controlled studies, 25% of TOPAMAX-treated patients discontinued due to adverse reactions, compared to 10% of the 445 placebo-treated patients.

Patients treated with TOPAMAX experienced mean percent reductions in body weight that were dose-dependent. This change was not seen in the placebo group. Mean changes of were seen for the placebo group, TOPAMAX 50, 100, and 200 mg groups, respectively.

Among adverse reactions with onset during titration, approximately half persisted into the maintenance period. In four, fixed-dose, double-blind clinical trials for the preventive treatment of migraine in TOPAMAX-treated pediatric patients 12 to 17 years of age, the most common adverse reactions with TOPAMAX 100 mg that were seen at an incidence higher (≥5%) than in the placebo group were: paresthesia, upper respiratory tract infection, anorexia, and abdominal pain (see Table 9 ). Table 9 also shows adverse reactions in pediatric patients in the controlled migraine trials when the incidence in a TOPAMAX dose group was at least 5% or higher and greater than the incidence of placebo.

Many adverse reactions shown in Table 9 indicate a dose-dependent relationship. The incidence of some adverse reactions (e.g., allergy, fatigue, headache, anorexia, insomnia, somnolence, and viral infection) was dose-related and greater at higher than recommended TOPAMAX dosing (200 mg daily) compared to the incidence of these adverse reactions at the recommended dosing (100 mg daily). Adverse reactions associated with discontinuing therapy that occurred in more than one TOPAMAX-treated patient were fatigue (1%), headache (1%), and somnolence (1%).

Increased Risk for Bleeding TOPAMAX 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 reaction for TOPAMAX than for placebo (4.5% versus 3.0% in adult patients, and 4.4% versus 2.3% in pediatric patients). Adverse bleeding reactions reported with TOPAMAX 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). Other Adverse Reactions Observed During Clinical Trials Other adverse reactions seen during clinical trials were: abnormal coordination, eosinophilia, gingival bleeding, hematuria, hypotension, myalgia, myopia, postural hypotension, scotoma, suicide attempt, syncope, and visual field defect. Laboratory Test Abnormalities Adult Patients In addition to changes in serum bicarbonate (i.e., metabolic acidosis), sodium chloride and ammonia, TOPAMAX was associated with changes in several clinical laboratory analytes in randomized, double-blind, placebo-controlled studies.

Pediatric Patients In pediatric patients (1–24 months) receiving adjunctive TOPAMAX for partial-onset seizures, there was an increased incidence for an increased result (relative to normal analyte reference range) associated with TOPAMAX (vs placebo) for the following clinical laboratory analytes: creatinine, blood urea nitrogen (BUN), alkaline phosphatase, and total protein, The incidence was also increased for a decreased result for bicarbonate (i.e., metabolic acidosis), and potassium with TOPAMAX (vs placebo). TOPAMAX is not indicated for partial-onset seizures in pediatric patients less than 2 years of age. In pediatric patients (ranging from 6–17 years of age) receiving TOPAMAX for the preventive treatment of migraine, there was an increased incidence for an increased result (relative to normal analyte reference range) associated with TOPAMAX (vs placebo) for the following clinical laboratory analytes: creatinine, BUN, uric acid, chloride, ammonia, alkaline phosphatase, total protein, platelets, and eosinophils, The incidence was also increased for a decreased result for phosphorus, bicarbonate, total white blood count, and neutrophils.

TOPAMAX is not indicated for the preventive treatment of migraine in pediatric patients less than 12 years of age.

Postmarketing Experience

The following adverse reactions have been identified during post approval use of TOPAMAX. 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. Body as a Whole-General Disorders: immediate hypersensitivity reactions (including anaphylaxis and angioedema), delayed hypersensitivity reactions (including facial swelling, lip swelling, periorbital swelling, tongue swelling), oligohydrosis and hyperthermia, hyperammonemia, hyperammonemic encephalopathy, hypothermia with concomitant valproic acid Gastrointestinal System Disorders: hepatic failure (including fatalities), hepatitis, pancreatitis Skin and Appendage Disorders: bullous skin reactions (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), pemphigus, urticaria Urinary System Disorders: kidney stones, nephrocalcinosis Vision Disorders: acute myopia, secondary angle closure glaucoma, maculopathy Hematological Disorders: decrease of the International Normalized Ratio (INR) or prothrombin time when given concomitantly with vitamin K antagonist anticoagulant medications such as warfarin.

Antiepileptic Drugs

Concomitant administration of phenytoin or carbamazepine with TOPAMAX resulted in a clinically significant decrease in plasma concentrations of topiramate when compared to TOPAMAX given alone. A dosage adjustment may be needed. Concomitant administration of valproic acid and TOPAMAX has been associated with hypothermia and hyperammonemia with and without encephalopathy.

Examine blood ammonia levels in patients in whom the onset of hypothermia has been reported.

Other Carbonic Anhydrase Inhibitors

Concomitant use of topiramate, a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., zonisamide or acetazolamide) may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation. Therefore, patients given TOPAMAX concomitantly with another carbonic anhydrase inhibitor should be monitored particularly closely for the appearance or worsening of metabolic acidosis.

CNS Depressants

Concomitant administration of TOPAMAX and alcohol or other CNS depressant drugs has not been evaluated in clinical studies. Because of the potential of topiramate to cause CNS depression, as well as other cognitive and/or neuropsychiatric adverse reactions, TOPAMAX should be used with extreme caution if used in combination with alcohol and other CNS depressants.

Contraceptives

The possibility of decreased contraceptive efficacy and increased breakthrough bleeding may occur in patients taking contraceptive products with TOPAMAX. Patients taking estrogen-containing or progestin-only contraceptives should be asked to report any change in their bleeding patterns. Contraceptive efficacy can be decreased even in the absence of breakthrough bleeding.

Hydrochlorothiazide (HCTZ) Topiramate

C max and AUC increased when HCTZ was added to TOPAMAX. The clinical significance of this change is unknown. The addition of HCTZ to TOPAMAX may require a decrease in the TOPAMAX dose.

Pioglitazone

A decrease in the exposure of pioglitazone and its active metabolites were noted with the concurrent use of pioglitazone and TOPAMAX in a clinical trial. The clinical relevance of these observations is unknown; however, when TOPAMAX is added to pioglitazone therapy or pioglitazone is added to TOPAMAX therapy, careful attention should be given to the routine monitoring of patients for adequate control of their diabetic disease state.

Lithium

An increase in systemic exposure of lithium following TOPAMAX doses of up to 600 mg/day can occur. Lithium levels should be monitored when co-administered with high-dose TOPAMAX.

Amitriptyline

Some patients may experience a large increase in amitriptyline concentration in the presence of TOPAMAX and any adjustments in amitriptyline dose should be made according to the patient's clinical response and not on the basis of plasma levels.

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to TOPAMAX 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 TOPAMAX can cause fetal harm when administered to a pregnant woman.

Data from pregnancy registries indicate that infants exposed to topiramate in utero have an increased risk of major congenital malformations, including but not limited to cleft lip and/or cleft palate (oral clefts), and of being small for gestational age (SGA). SGA has been observed at all doses and appears to be dose-dependent. The prevalence of SGA is greater in infants of women who received higher doses of topiramate during pregnancy.

In addition, the prevalence of SGA in infants of women who continued topiramate use until later in pregnancy is higher compared to the prevalence in infants of women who stopped topiramate use before the third trimester. In multiple animal species, topiramate produced developmental toxicity, including increased incidences of fetal malformations, in the absence of maternal toxicity at clinically relevant doses. All pregnancies have a background risk of birth defects, loss, or other adverse outcomes.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2–4% and 15–20%, respectively. Clinical Considerations Fetal/Neonatal Adverse Reactions Consider the benefits and risks of topiramate when prescribing this drug to women of childbearing potential, particularly when topiramate is considered for a condition not usually associated with permanent injury or death.

Because of the risk of oral clefts to the fetus, which occur in the first trimester of pregnancy, all women of childbearing potential should be informed of the potential risk to the fetus from exposure to topiramate. Women who are planning a pregnancy should be counseled regarding the relative risks and benefits of topiramate use during pregnancy, and alternative therapeutic options should be considered for these patients. Labor or Delivery Although the effect of TOPAMAX on labor and delivery in humans has not been established, the development of topiramate-induced metabolic acidosis in the mother and/or in the fetus might affect the fetus' ability to tolerate labor.

TOPAMAX treatment can cause metabolic acidosis. The effect of topiramate-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus' ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state.

Newborns of mothers treated with TOPAMAX should be monitored for metabolic acidosis because of transfer of topiramate to the fetus and possible occurrence of transient metabolic acidosis following birth. Based on limited information, topiramate has also been associated with pre-term labor and premature delivery. Data Human Data Data from pregnancy registries indicate an increased risk of major congenital malformations, including but not limited to oral clefts in infants exposed to topiramate during the first trimester of pregnancy.

Other than oral clefts, no specific pattern of major congenital malformations or grouping of major congenital malformation types were observed. In the NAAED pregnancy registry, when topiramate-exposed infants with only oral clefts were excluded, the prevalence of major congenital malformations (4.1%) was higher than that in infants exposed to a reference AED (1.8%) or in infants with mothers without epilepsy and without exposure to AEDs (1.1%). The prevalence of oral clefts among topiramate-exposed infants (1.4%) was higher than the prevalence in infants exposed to a reference AED (0.3%) or the prevalence in infants with mothers without epilepsy and without exposure to AEDs (0.11%).

It was also higher than the background prevalence in United States (0.17%) as estimated by the Centers for Disease Control and Prevention (CDC). The relative risk of oral clefts in topiramate-exposed pregnancies in the NAAED Pregnancy Registry was 12.5 (95% Confidence Interval 5.9–26.37) as compared to the risk in a background population of untreated women. The UK Epilepsy and Pregnancy Register reported a prevalence of oral clefts among infants exposed to topiramate monotherapy (3.2%) that was 16 times higher than the background rate in the UK (0.2%).

Data from the NAAED pregnancy registry and a population-based birth registry cohort indicate that exposure to topiramate in utero is associated with an increased risk of SGA newborns (birth weight <10th percentile). In the NAAED pregnancy registry, 19.7% of topiramate-exposed newborns were SGA compared to 7.9% of newborns exposed to a reference AED and 5.4% of newborns of mothers without epilepsy and without AED exposure. In the Medical Birth Registry of Norway (MBRN), a population-based pregnancy registry, 25% of newborns in the topiramate monotherapy exposure group were SGA compared to 9% in the comparison group unexposed to AEDs.

The long-term consequences of the SGA findings are not known. Animal Data When topiramate mg/kg/day was administered to pregnant mice during the period of organogenesis, incidences of fetal malformations (primarily craniofacial defects) were increased at all doses. Fetal body weights and skeletal ossification were reduced at the highest dose tested in conjunction with decreased maternal body weight gain.

A no-effect dose for embryofetal developmental toxicity in mice was not identified. The lowest dose tested, which was associated with increased malformations, is less than the maximum recommended human dose (MRHD) for epilepsy (400 mg/day) or migraine (100 mg/day) on a body surface area (mg/m 2 ) basis. In pregnant rats administered topiramate mg/kg/day or mg/kg/day orally during the period of organogenesis, the frequency of limb malformations (ectrodactyly, micromelia, and amelia) was increased in fetuses at 400 and 500 mg/kg/day.

Embryotoxicity (reduced fetal body weights, increased incidences of structural variations) was observed at doses as low as 20 mg/kg/day. Clinical signs of maternal toxicity were seen at 400 mg/kg/day and above, and maternal body weight gain was reduced at doses of 100 mg/kg/day or greater. The no-effect dose (2.5 mg/kg/day) for embryofetal developmental toxicity in rats is less than the MRHD for epilepsy or migraine on a mg/m 2 basis.

In pregnant rabbits administered topiramate mg/kg/day or mg/kg/day orally during organogenesis, embryofetal mortality was increased at 35 mg/kg/day, and increased incidences of fetal malformations (primarily rib and vertebral malformations) were observed at 120 mg/kg/day. Evidence of maternal toxicity (decreased body weight gain, clinical signs, and/or mortality) was seen at 35 mg/kg/day and above. The no-effect dose (20 mg/kg/day) for embryofetal developmental toxicity in rabbits is equivalent to the MRHD for epilepsy and approximately 4 times the MRHD for migraine on a mg/m 2 basis.

When topiramate mg/kg/day or mg/kg/day was administered orally to female rats during the latter part of gestation and throughout lactation, offspring exhibited decreased viability and delayed physical development at 200 mg/kg/day and reductions in pre- and/or postweaning body weight gain at 2 mg/kg/day and above. Maternal toxicity (decreased body weight gain, clinical signs) was evident at 100 mg/kg/day or greater. In a rat embryofetal development study which included postnatal assessment of offspring, oral administration of topiramate mg/kg to pregnant animals during the period of organogenesis resulted in delayed physical development in offspring at 400 mg/kg/day and persistent reductions in body weight gain in offspring at 30 mg/kg/day and higher.

Pediatric Use Adjunctive Treatment for Epilepsy Pediatric Patients 2 Years of Age and Older The safety and effectiveness of TOPAMAX as adjunctive therapy for the treatment of partial-onset seizures, primary generalized tonic-clonic seizures, or seizures associated with Lennox-Gastaut syndrome have been established in pediatric patients 2 years of age and older. In a single randomized, double-blind, placebo-controlled investigational trial, the efficacy, safety, and tolerability of topiramate oral liquid and sprinkle formulations as an adjunct to concurrent antiepileptic drug therapy in pediatric patients 1 to 24 months of age with refractory partial-onset seizures were assessed. In general, the adverse reaction profile for TOPAMAX 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 pediatric patients 1 to 24 months old suggested some adverse reactions/toxicities (not previously observed in older pediatric patients and adults; i.e., growth/length retardation, certain clinical laboratory abnormalities, and other adverse reactions/toxicities 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).

The following adverse reactions were observed in at least 3% of patients on 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. 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.

The significance of these findings is uncertain. 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. There was a mean dose-related increase in alkaline phosphatase.

Topiramate produced a dose-related increased incidence of hyperammonemia. Treatment with topiramate for up to 1 year was associated with reductions in Z SCORES for length, weight, and head circumference. 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). 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 topiramate treatment, because the background mortality rate for a similar, significantly refractory, young pediatric population (1–24 months) with partial epilepsy is not known. A one-year, active-controlled, open-label study with blinded assessments of bone mineral density (BMD) and growth in pediatric patients 4 to 15 years of age, including 63 patients with recent or new onset of epilepsy, was conducted to assess effects of TOPAMAX (N=28, 6–15 years of age) versus levetiracetam (N=35, 4–15 years of age) monotherapy on bone mineralization and on height and weight, which reflect growth. Effects on bone mineralization were evaluated via dual-energy X-ray absorptiometry and blood markers.

Table 10 summarizes effects of TOPAMAX at 12 months for key safety outcomes including BMD, height, height velocity, and weight. All Least Square Mean values for TOPAMAX and the comparator were positive. Therefore, the Least Square Mean treatment differences shown reflect a TOPAMAX-induced attenuation of the key safety outcomes.

Statistically significant effects were observed for decreases in BMD (and bone mineral content) in lumbar spine and total body less head and in weight. Subgroup analyses according to age demonstrated similar negative effects for all key safety outcomes (i.e., BMD, height, weight). Over the whole study, 76% more TOPAMAX-treated patients experienced persistent metabolic acidosis (i.e. 2 consecutive visits with or final serum bicarbonate < 20 mEq/L) compared to levetiracetam -treated patients.

Over the whole study, 35% more TOPAMAX-treated patients experienced a markedly abnormally low serum bicarbonate (i.e., absolute value < 17 mEq/L and ≥ 5 mEq/L decrease from pre-treatment), indicating the frequency of more severe metabolic acidosis, compared to levetiracetam -treated patients. The decrease in BMD at 12 months was correlated with decreased serum bicarbonate, suggesting that metabolic acidosis was at least a partial factor contributing to this adverse effect on BMD. TOPAMAX-treated patients exhibited an increased risk for developing an increased serum creatinine and an increased serum glucose above the normal reference range compared to control patients.

Pediatric Patients Below the Age of 2 Years Safety and effectiveness in patients below the age of 2 years have not been established for the monotherapy treatment of epilepsy. 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. In the pediatric trials (12 to 17 years of age) in which patients were randomized to placebo or a fixed daily dose of TOPAMAX, the most common adverse reactions with TOPAMAX that were seen at an incidence higher (≥5%) than in the placebo group were: paresthesia, upper respiratory tract infection, anorexia, and abdominal pain.

The most common cognitive adverse reaction in pooled double-blind studies in pediatric patients 12 to 17 years of age was difficulty with concentration/attention. Markedly abnormally low serum bicarbonate values indicative of metabolic acidosis were reported in topiramate-treated pediatric migraine patients. In topiramate-treated pediatric patients (12 to 17 years of age) 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. Notable changes (increases and decreases) from baseline in systolic blood pressure, diastolic blood pressure, and pulse were observed occurred more commonly in pediatric patients treated with topiramate compared to pediatric patients treated with placebo. Pediatric Patients Below the Age of 12 Years Safety and effectiveness in pediatric patients below the age of 12 years have not been established for the preventive treatment of migraine.

Difficulty with concentration/attention occurred in 3 topiramate-treated patients (5%) and 0 placebo-treated patients. Juvenile Animal Studies When topiramate 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.

TOPAMAX is contraindicated in patients with a history of hypersensitivity reaction to topiramate, TOPAMAX, or any of the inactive ingredients of TOPAMAX. Anaphylaxis and angioedema have occurred.

Overdoses of TOPAMAX have been reported. Signs and symptoms included convulsions, drowsiness, speech disturbance, blurred vision, diplopia, impaired mentation, lethargy, abnormal coordination, stupor, hypotension, abdominal pain, agitation, dizziness and depression. The clinical consequences were not severe in most cases, but deaths have been reported after overdoses involving TOPAMAX.

TOPAMAX overdose has resulted in severe metabolic acidosis. In the event of overdose, TOPAMAX should be discontinued and general supportive treatment given until clinical toxicity has been diminished or resolved. Hemodialysis is an effective means of removing topiramate from the body.