Topiramate

QUDEXY XR is indicated for: Epilepsy: initial monotherapy for the treatment of partial-onset or primary generalized tonic-clonic seizures in patients 2 years of age and older ( 1.1 ); adjunctive therapy for the treatment of partial-onset seizures, primary generalized tonic-clonic seizures, or seizures associated with Lennox-Gastaut Syndrome in patients 2 years of age and older ( 1.2 ) Preventive treatment of migraine in patients 12 years of age and older ( 1.3 )

1.1 Monotherapy Epilepsy QUDEXY XR 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.

1.2 Adjunctive Therapy Epilepsy QUDEXY XR 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.

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

QUDEXY XR (topiramate) extended-release capsules are available in the following strengths and colors: 25 mg: light pink and grey capsules, printed with "UPSHER-SMITH" on the cap in black ink and "25 mg" on the body in black ink 50 mg: golden yellow and grey capsules, printed with "UPSHER-SMITH" on the cap in black ink and "50 mg" on the body in black ink 100 mg: reddish brown and grey capsules, printed with "UPSHER-SMITH" on the cap in black ink and "100 mg" on the body in black ink 150 mg: pale yellow and grey capsules, printed with "UPSHER-SMITH" on the cap in black ink and "150 mg" on the body in black ink 200 mg: brown and grey capsules, printed with "UPSHER-SMITH" on the cap in white ink and "200 mg" on the body in black ink Extended-release capsules: 25 mg, 50 mg, 100 mg, 150 mg, and 200 mg ( 3 )

QUDEXY XR is contraindicated in patients with a history of hypersensitivity reaction to topiramate, QUDEXY XR, or any of the inactive ingredients of QUDEXY XR. Anaphylaxis and angioedema have occurred with topiramate [see Warnings and Precautions (5.14) ]. History of hypersensitivity reaction to topiramate, QUDEXY XR, or any of the inactive ingredients of QUDEXY XR (4, 5.13)

Acute myopia and secondary angle closure glaucoma: can lead to permanent visual loss; discontinue QUDEXY XR as soon as possible ( 5.1 ) Visual field defects: consider discontinuation of QUDEXY XR ( 5.2 ) Oligohydrosis and hyperthermia: monitor decreased sweating and increased body temperature, especially in pediatric patients ( 5.3 ) Metabolic acidosis: baseline and periodic measurement of serum bicarbonate is recommended; consider dose reduction or discontinuation of QUDEXY XR if clinically appropriate ( 5.4 ) Suicidal behavior and ideation: antiepileptic drugs increase the risk of suicidal behavior or ideation ( 5.5 ) Cognitive/neuropsychiatric adverse reactions: use caution when operating machinery including cars; depression and mood problems may occur ( 5.6 ) Cardiac Rhythm and Conduction Abnormalities: can cause cardiac rhythm and conduction abnormalities, particularly in patients with underlying cardiac disorders or arrhythmias ( 5.7 ). Fetal Toxicity: use during pregnancy can cause major congenital malformations, including but not limited to cleft lip and/or palate and being small for gestational age ( 5.8 ) Withdrawal of AEDs: withdraw QUDEXY XR gradually ( 5.9 ) Decrease in Bone Mineral Density: has been shown to decrease bone mineral density and bone mineral content in pediatric patients ( 5.10 ) Negative effects on growth (height and weight): may slow height increase and weight gain; carefully monitor children receiving prolonged therapy ( 5.11 ) Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity, serious skin reactions, anaphylaxis, and angioedema: Discontinue QUDEXY XR if an alternative etiology cannot be established. ( 5.12, 5.13 , 5.14 ) Hyperammonemia/encephalopathy: measure ammonia if encephalopathic symptoms occur ( 5.15 ) Kidney stones: avoid use with other carbonic anhydrase inhibitors, drugs causing metabolic acidosis, or in patients on a ketogenic diet ( 5.16 ) Hypothermia has been reported with and without hyperammonemia during topiramate treatment with concomitant valproic acid use ( 5.17 )

5.1 Acute Myopia and Secondary Angle Closure Glaucoma Syndrome A syndrome consisting of acute myopia associated with secondary angle closure glaucoma has been reported in patients receiving topiramate. Symptoms include acute onset of decreased visual acuity and/or ocular pain. Ophthalmologic findings can include some or all of the following: myopia, mydriasis, anterior chamber shallowing, ocular hyperemia (redness), choroidal detachments, retinal pigment epithelial detachments, macular striae, and increased intraocular pressure. This syndrome may be associated with supraciliary effusion resulting in anterior displacement of the lens and iris, with secondary angle closure glaucoma. Symptoms typically occur within 1 month of initiating topiramate therapy. In contrast to primary narrow angle glaucoma, which is rare under 40 years of age, secondary angle closure glaucoma associated with topiramate has been reported in pediatric patients as well as adults. The primary treatment to reverse symptoms is discontinuation of QUDEXY XR as rapidly as possible, according to the judgment of the treating physician. Other measures, in conjunction with discontinuation of QUDEXY XR, may be helpful. Elevated intraocular pressure of any etiology, if left untreated, can lead to serious sequelae including permanent vision loss.

5.2 Visual Field Defects Visual field defects (independent of elevated intraocular pressure) have been reported in clinical trials and in postmarketing experience in patients receiving topiramate independent of elevated intraocular pressure. In clinical trials, most of these events were reversible after topiramate discontinuation. If visual problems occur at any time during treatment with topiramate, consideration should be given to discontinuing the drug.

5.3 Oligohydrosis and Hyperthermia Oligohydrosis (decreased sweating), infrequently resulting in hospitalization in some cases, has been reported in association with topiramate use. Decreased sweating and an elevation in body temperature above normal characterized these cases. Some of the cases were reported after exposure to elevated environmental temperatures. The majority of the reports have been in pediatric patients. Patients (especially pediatric patients) treated with QUDEXY XR should be monitored closely for evidence of decreased sweating and increased body temperature, especially in hot weather. Caution should be used when QUDEXY XR is prescribed with other drugs that predispose patients to heat-related disorders; these drugs include, but are not limited to, other carbonic anhydrase inhibitors and drugs with anticholinergic activity.

5.4 Metabolic Acidosis QUDEXY XR can cause hyperchloremic, non-anion gap, metabolic acidosis (i.e., decreased serum bicarbonate below the normal reference range in the absence of chronic respiratory alkalosis). This metabolic acidosis is caused by renal bicarbonate loss due to carbonic anhydrase inhibition by QUDEXY XR. QUDEXY XR-induced metabolic acidosis can occur at any time during treatment. Bicarbonate decrements are usually mild to moderate (average decrease of 4 mEq/L at daily doses of 400 mg in adults and at approximately 6 mg/kg/day in pediatric patients); rarely, patients can experience severe decrements to values below 10 mEq/L. Conditions or therapies that predispose patients to acidosis (such as renal disease, severe respiratory disorders, status epilepticus, diarrhea, ketogenic diet or specific drugs) may be additive to the bicarbonate lowering effects of QUDEXY XR. Metabolic acidosis was commonly observed in adult and pediatric patients treated with immediate-release topiramate in clinical trials. The incidence of decreased serum bicarbonate in pediatric trials, for adjunctive treatment of Lennox-Gastaut syndrome or refractory partial-onset seizures was as high as 67% for immediate-release topiramate (at approximately 6 mg/kg/day), and 10% for placebo. The incidence of a markedly abnormally low serum bicarbonate (i.e., absolute value < 17 mEq/L and ≥5 mEq/L decrease from pretreatment) in these trials was up to 11%, compared to ≤ 2% for placebo. 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 [see Warnings and Precautions ( 5.10 , 5.14) ] . A one-year, active-controlled study of pediatric patients treated with immediate-release topiramate demonstrated that topiramate decreased lumbar spine bone mineral density and that this lumbar spine bone mineral density decrease was correlated (using change from baseline for lumbar spine Z score at final visit versus lowest post-treatment serum bicarbonate) with decreased serum bicarbonate, a reflection of metabolic acidosis [see Warnings and Precautions (5.10) , Use in Specific Populations (8.4) ] . Chronic metabolic acidosis in pediatric patients may also reduce growth rates, which may decrease the maximal height achieved. Long-term, open-label treatment of pediatric patients 1 to 24 months old with intractable partial epilepsy, for up to 1 year, showed reductions from baseline in 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 1 to 24-months old patients. Reductions in length and weight were correlated to the degree of acidosis [see Use in Specific Populations (8.4) ] . […]

The following serious adverse reactions are discussed in more detail in other sections of the labeling: Acute Myopia and Secondary Angle Closure Glaucoma [see Warnings and Precautions (5.1) ] Visual Field Defects [see Warnings and Precautions (5.2) ] Oligohydrosis and Hyperthermia [see Warnings and Precautions (5.3) ] Metabolic Acidosis [see Warnings and Precautions (5.4) ] Suicidal Behavior and Ideation [see Warnings and Precautions (5.5) ] Cognitive/Neuropsychiatric Adverse Reactions [see Warnings and Precautions (5.6) ] Cardiac Rhythm and Conduction Abnormalities [see Warnings and Precautions (5.7 )] Decrease in Bone Mineral Density [see Warnings and Precautions (5.10) ] Negative Effects on Growth (Height and Weight) [see Warnings and Precautions (5.11) ] Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan

• Hypersensitivity Reactions [see Warnings and Precautions (5.12) ] Serious Skin Reactions [see Warnings and Precautions (5.13) ] Anaphylaxis and Angioedema [see Warnings and Precautions (5.14) ] Hyperammonemia and Encephalopathy (Without and With Concomitant Valproic Acid Use [see Warnings and Precautions (5.15) ] Kidney Stones [see Warnings and Precautions (5.16) ] Hypothermia with Concomitant Valproic Acid Use [see Warnings and Precautions (5.17) ] The data described in section 6.1 were obtained using immediate-release topiramate tablets. Epilepsy : The most common (≥10% more frequent than placebo or low-dose topiramate) adverse reactions in adult and pediatric patients were: paresthesia, anorexia, weight loss, speech disorders/related speech problems, fatigue, dizziness, somnolence, nervousness, psychomotor slowing, abnormal vision and fever ( 6.1 ) Migraine : Most common (≥5% more frequent than placebo) adverse reactions in adult and pediatric patients were: paresthesia, anorexia, weight loss, difficulty with memory, taste perversion, diarrhea, hypoesthesia, nausea, abdominal pain and upper respiratory tract infection ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Upsher-Smith Laboratories, LLC at 1-855-899-9180 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch

6.1 Clinical Trials Experience with Immediate-Release Topiramate 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 clinical practice. Monotherapy Epilepsy Adults 16 Years of Age and Older The most common adverse reactions in the controlled trial (Study 1) that occurred in adults in the 400 mg/day topiramate group and at an incidence higher (≥ 10%) than in the 50 mg/day group were: paresthesia, weight loss, and anorexia (see Table 5 ) . Approximately 21% of the 159 adult patients in the 400 mg/day group who received topiramate as monotherapy in Study 1 discontinued therapy due to adverse reactions. The most common (≥ 2% more frequent than low-dose 50 mg/day topiramate) adverse reactions causing discontinuation were difficulty with memory, fatigue, asthenia, insomnia, somnolence, and paresthesia. Pediatric Patients 6 to 15 Years of Age The most common adverse reactions in the controlled trial (Study 1) that occurred in pediatric patients in the 400 mg/day topiramate group and at an incidence higher (≥ 10%) than in the 50 mg/day group were fever and weight loss (see Table 5 ). Approximately 14% of the 77 pediatric patients in the 400 mg/day group who received topiramate as monotherapy in the controlled clinical trial discontinued therapy due to adverse reactions. The most common (≥ 2% more frequent than in the 50 mg/day group) adverse reactions resulting in discontinuation in this trial were difficulty with concentration/attention, fever, flushing, and confusion. Table 5 represents the incidence of adverse reactions occurring in at least 3% of the adult and pediatric patients treated with 400 mg/day immediate-release topiramate and occurring with greater incidence than 50 mg/day topiramate. Table 5: Adverse Reactions in the High Dose Group as Compared to the Low Dose Group, in Monotherapy Epilepsy Trials (Study 1) in Adult and Pediatric Patients Age Group Pediatric (6 to 15 Years) Adult (Age ≥16 Years) Immediate-release Topiramate Daily Dosage Group (mg/day) 50 400 50 400 Body System/ Adverse Reaction (N=74) % (N=77) % (N=160) % (N=159) % Body as a Whole-General Disorders Asthenia 0 3 4 6 Fever 1 12 Leg pain 2 3 Central & Peripheral Nervous System Disorders Paresthesia 3 12 21 40 Dizziness 13 14 Ataxia 3 4 Hypoesthesia 4 5 Hypertonia 0 3 Involuntary muscle contraction 0 3 Vertigo 0 3 Gastro-Intestinal System Disorders Constipation 1 4 Diarrhea 8 9 Gastritis 0 3 Dry mouth 1 3 Liver and Biliary System Disorders Increase in gamma-GT 1 3 Metabolic and Nutritional Disorders Weight loss 7 17 6 17 Platelet, Bleeding & Clotting Disorders Epistaxis 0 4 Psychiatric Disorders Anorexia 4 14 Anxiety 4 6 Cognitive problems 1 6 1 4 Confusion 0 3 Depression 0 3 7 9 Difficulty with concentration or attention 7 10 7 8 Difficulty with memory 1 3 6 11 Insomnia 8 9 Decrease in libido 0 3 Mood problems 1 8 2 5 Personality disorder (behavior problems) 0 3 Psychomotor slowing 3 5 Somnolence 10 15 Red Blood Cell Disorders Anemia 1 3 Reproductive Disorders, Female Intermenstrual bleeding 0 3 Vaginal hemorrhage 0 3 Resistance Mechanism Disorders Infection 3 8 2 3 Viral infection 3 6 6 8 Respiratory System Disorders Bronchitis 1 5 3 4 Upper respiratory tract infection 16 18 Rhinitis 5 6 2 4 Sinusitis 1 4 Skin and Appendages Disorders Alopecia 1 4 3 4 Pruritus 1 4 Rash 3 4 1 4 Acne 2 3 Special Senses Other, Disorders Taste perversion 3 5 Urinary System Disorders Cystitis 1 3 Micturition frequency 0 3 Renal calculus 0 3 Urinary incontinence 1 3 Vascular (Extracardiac) Disorders Flushing 0 5 Adjunctive Therapy Epilepsy .Adults 16 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 immediate-release topiramate 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 immediate-release topiramate or placebo. The most common adverse reactions in the controlled clinical trial that occurred in adult patients in the 200 to 400 mg/day topiramate 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). Table 6 presents the incidence of adverse reactions occurring in at least 3% of adult patients treated with 200 to 400 mg/day topiramate and was greater than placebo incidence. 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 topiramate dosing (i.e., 600 mg to 1000 mg daily) compared to the incidence of these adverse reactions at the recommended dosing (200 mg to 400 mg daily) range. Table 6: Most Common Adverse Reactions in Pooled Placebo-Controlled, Adjunctive Epilepsy Trials in Adults Patients in these adjunctive trials were receiving 1 to 2 concomitant antiepileptic drugs in addition to topiramate or placebo. […]

Oral contraceptives: decreased contraceptive efficacy and increased breakthrough bleeding, especially at doses greater than 200 mg per day ( 7.4 ) Monitor lithium levels if lithium is used with high-dose QUDEXY XR ( 7.7 )

7.1 Antiepileptic Drugs Concomitant administration of phenytoin or carbamazepine with topiramate resulted in a clinically significant decrease in plasma concentrations of topiramate when compared to topiramate given alone. A dosage adjustment may be needed [see Clinical Pharmacology (12.3) ] . Concomitant administration of valproic acid and topiramate 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 [see Warnings and Precautions (5.12 , 5.14) , Clinical Pharmacology (12.3) ].

7.2 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. Patients should be monitored for the appearance or worsening of metabolic acidosis when QUDEXY XR is given concomitantly with another carbonic anhydrase inhibitor [see Clinical Pharmacology (12.3) ]. 7.3 CNS Depressants Concomitant administration of topiramate 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, QUDEXY XR should be used with extreme caution if used in combination with alcohol and other CNS depressants.

7.4 Contraceptives The possibility of decreased contraceptive efficacy and increased breakthrough bleeding may occur in patients taking contraceptive products with QUDEXY XR. 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 [see Clinical Pharmacology (12.3) ] .

7.5 Hydrochlorothiazide (HCTZ) Topiramate C max and AUC increased when HCTZ was added to immediate-release topiramate. The clinical significance of this change is unknown. The addition of HCTZ to QUDEXY XR may require a decrease in the QUDEXY XR dose [see Clinical Pharmacology (12.3) ] .

7.6 Pioglitazone A decrease in the exposure of pioglitazone and its active metabolites were noted with the concurrent use of pioglitazone and immediate-release topiramate in a clinical trial. The clinical relevance of these observations is unknown; however, when QUDEXY XR is added to pioglitazone therapy or pioglitazone is added to QUDEXY XR therapy, careful attention should be given to the routine monitoring of patients for adequate control of their diabetic disease state [see Clinical Pharmacology (12.3) ] .

7.7 Lithium An increase in systemic exposure of lithium following topiramate doses of up to 600 mg/day can occur. Lithium levels should be monitored when co-administered with high-dose QUDEXY XR [see Clinical Pharmacology (12.3) ] .

7.8 Amitriptyline Some patients may experience a large increase in amitriptyline concentration in the presence of QUDEXY XR and any adjustments in amitriptyline dose should be made according to the patient's clinical response and not on the basis of plasma levels [see Clinical Pharmacology (12.3) ] .

8.1 Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as QUDEXY XR, 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 QUDEXY XR 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 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) [see Human Data ]. 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 demonstrated developmental toxicity, including increased incidences of fetal malformations, in the absence of maternal toxicity at clinically relevant doses [see Animal Data ] . 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% to 4% and 15% to 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 before many women know they are pregnant, 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 topiramate 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 . QUDEXY XR treatment can cause metabolic acidosis [see Warnings and Precautions (5.4) ]. 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 [see Warnings and Precautions (5.4) ]. Newborns of mothers treated with QUDEXY XR 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 the 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=[CI] 5.9 to 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 who were unexposed to AEDs. The long-term consequences of the SGA findings are not known. Animal Data When topiramate (0, 20, 100, or 500 mg/kg/day) was administered orally to pregnant mice during the period of organogenesis, the incidence 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 an increased incidence of 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 (0, 20, 100, and 500 mg/kg/day or 0, 0.2, 2.5, 30, and 400 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 (0, 20, 60, and 180 mg/kg/day or 0, 10, 35, and 120 mg/kg/day) orally during organogenesis, embryofetal mortality was increased at 35 mg/kg/day and an increased incidence of fetal malformations (primarily rib and vertebral malformations) was 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 precise mechanisms by which topiramate exerts its anticonvulsant and preventive migraine effects are unknown; however, preclinical studies have revealed four properties that may contribute to topiramate's efficacy for epilepsy and the preventive treatment of migraine. Electrophysiological and biochemical evidence suggests that topiramate, at pharmacologically relevant concentrations, blocks voltage-dependent sodium channels, augments the activity of the neurotransmitter gamma-aminobutyrate at some subtypes of the GABA-A receptor, antagonizes the AMPA/kainate subtype of the glutamate receptor, and inhibits the carbonic anhydrase enzyme, particularly isozymes II and IV.