DailyMed Label: Zonisamide

DailyMed Label: Zonisamide

2024

DailyMed Prescription

Zonisamide

Zonisamide

American Health Packaging

NDC: 60687-230

NDC: 60687-230

NDC: 60687-230

Zonisamide, USP is an antiseizure drug chemically classified as a sulfonamide and unrelated to other antiseizure agents. The active ingredient is zonisamide USP, 1,2-benzisoxazole-3-methanesulfonamide. The empirical formula is C 8 H 8 N 2 O 3 S with a molecular weight of 212.23. Zonisamide USP is a white powder, pKa = 10.2, and is moderately soluble in water (0.80 mg/mL) and 0.1 N HCl (0.50 mg/mL). The chemical structure is: Zonisamide is supplied for oral administration as capsules containing 100 mg zonisamide. Each 100 mg capsule contains the labeled amount of zonisamide plus the following inactive ingredients: microcrystalline cellulose, hydrogenated vegetable oil, gelatin and colorants. Components of gelatin capsules (For 100 mg: titanium dioxide, gelatin and FDA/E172 red iron oxide). Imprint ink dye (Black SW- 9008/SW-9009). Structural Formula

Zonisamide capsules are indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.

Zonisamide, USP is recommended as adjunctive therapy for the treatment of partial seizures in adults. Safety and efficacy in pediatric patients below the age of 16 have not been established. Zonisamide should be administered once or twice daily, using 25 mg or 100 mg capsules. Zonisamide is given orally and can be taken with or without food. Capsules should be swallowed whole. Adults over Age 16: The prescriber should be aware that, because of the long half-life of zonisamide, up to two weeks may be required to achieve steady state levels upon reaching a stable dose or following dosage adjustment. Although the regimen described below is one that has been shown to be tolerated, the prescriber may wish to prolong the duration of treatment at the lower doses in order to fully assess the effects of zonisamide at steady state, noting that many of the side effects of zonisamide are more frequent at doses of 300 mg per day and above. Although there is some evidence of greater response at doses above 100 to 200 mg/day, the increase appears small and formal dose-response studies have not been conducted. The initial dose of zonisamide should be 100 mg daily. After two weeks, the dose may be increased to 200 mg/day for at least two weeks. It can be increased to 300 mg/day and 400 mg/day, with the dose stable for at least two weeks to achieve steady state at each level. Evidence from controlled trials suggests that zonisamide doses of 100 to 600 mg/day are effective, but there is no suggestion of increasing response above 400 mg/day (see CLINICAL PHARMACOLOGY, Clinical Studies subsection). There is little experience with doses greater than 600 mg/day. Patients with Renal or Hepatic Disease: Because zonisamide is metabolized in the liver and excreted by the kidneys, patients with renal or hepatic disease should be treated with caution, and might require slower titration and more frequent monitoring (see CLINICAL PHARMACOLOGY and PRECAUTIONS ).

Zonisamide capsules are contraindicated in patients who have demonstrated hypersensitivity to sulfonamides or zonisamide.

Somnolence is commonly reported, especially at higher doses of zonisamide (see WARNINGS: Cognitive/ Neuropsychiatric Adverse Events subsection). Zonisamide is metabolized by the liver and eliminated by the kidneys; caution should therefore be exercised when administering zonisamide to patients with hepatic and renal dysfunction (see CLINICAL PHARMACOLOGY, Specific Populations subsection). Among 991 patients treated during the development of zonisamide, 40 patients (4.0%) with epilepsy receiving zonisamide developed clinically possible or confirmed kidney stones (e.g. clinical symptomatology, sonography, etc.), a rate of 34 per 1000 patient-years of exposure (40 patients with 1168 years of exposure). Of these, 12 were symptomatic, and 28 were described as possible kidney stones based on sonographic detection. In nine patients, the diagnosis was confirmed by a passage of a stone or by a definitive sonographic finding. The rate of occurrence of kidney stones was 28.7 per 1000 patient-years of exposure in the first six months, 62.6 per 1000 patient-years of exposure between 6 and 12 months, and 24.3 per 1000 patient-years of exposure after 12 months of use. There are no normative sonographic data available for either the general population or patients with epilepsy. Although the clinical significance of the sonographic findings may not be certain, the development of nephrolithiasis may be related to metabolic acidosis (see WARNINGS, Metabolic Acidosis subsection). The analyzed stones were composed of calcium or urate salts. In general, increasing fluid intake and urine output can help reduce the risk of stone formation, particularly in those with predisposing risk factors. It is unknown, however, whether these measures will reduce the risk of stone formation in patients treated with zonisamide. Although not approved in pediatric patients, sonographic findings consistent with nephrolithiasis were also detected in 8% of a subset of zonisamide treated pediatric patients who had at least one renal ultrasound prospectively performed in a clinical development program investigating open-label treatment. The incidence of kidney stone as an adverse event was 3% (see WARNINGS, Metabolic Acidosis subsection). In several clinical studies, zonisamide was associated with a statistically significant 8% mean increase from baseline of serum creatinine and blood urea nitrogen (BUN) compared to essentially no change in the placebo patients. The increase appeared to persist over time but was not progressive; this has been interpreted as an effect on glomerular filtration rate (GFR). There were no episodes of unexplained acute renal failure in clinical development in the US, Europe, or Japan. The decrease in GFR appeared within the first 4 weeks of treatment. In a 30-day study, the GFR returned to baseline within 2 to 3 weeks of drug discontinuation. There is no information about reversibility, after drug discontinuation, of the effects on GFR after long-term use. Zonisamide should be discontinued in patients who develop acute renal failure or a clinically significant sustained increase in the creatinine/BUN concentration. Zonisamide should not be used in patients with renal failure (estimated GFR < 50 mL/min) as there has been insufficient experience concerning drug dosing and toxicity. Estimates of the incidence of treatment emergent status epilepticus in zonisamide-treated patients are difficult because a standard definition was not employed. Nonetheless, in controlled trials, 1.1% of patients treated with zonisamide had an event labeled as status epilepticus compared to none of the patients treated with placebo. Among patients treated with zonisamide across all epilepsy studies (controlled and uncontrolled), 1.0% of patients had an event reported as status epilepticus. Inform patients of the availability of a Medication Guide, and instruct them to read the Medication Guide prior to taking zonisamide. Instruct patients to take zonisamide only as prescribed. Advise patients as follows: (See Medication Guide ) Zonisamide may produce drowsiness, especially at higher doses. Patients should be advised not to drive a car or operate other complex machinery until they have gained experience on zonisamide sufficient to determine whether it affects their performance. Because of the potential of zonisamide to cause CNS depression, as well as other cognitive and/or neuropsychiatric adverse events, zonisamide should be used with caution if used in combination with alcohol or other CNS depressants. Patients should contact their physician immediately if a skin rash develops (see WARNINGS, Serious Skin Reactions subsection). Instruct patients to seek immediate medical attention if they experience blurred vision, visual disturbances, or periorbital pain (see WARNINGS, Acute Myopia and Secondary Angle Closure Glaucoma subsection). Patients should contact their physician immediately if they develop signs or symptoms, such as sudden back pain, abdominal pain, and/or blood in the urine, that could indicate a kidney stone. Increasing fluid intake and urine output may reduce the risk of stone formation, particularly in those with predisposing risk factors for stones (see PRECAUTIONS, Kidney Stones subsection). Patients should contact their physician immediately if a child has been taking zonisamide and is not sweating as usual with or without a fever (see WARNINGS, Oligohidrosis and Hyperthermia in Pediatric Patients subsection). Because zonisamide can cause hematological complications, patients should contact their physician immediately if they develop a fever, sore throat, oral ulcers, or easy bruising (see WARNINGS, Serious Hematologic Events subsection). Counsel patients and caregivers that AEDs, including zonisamide, may increase the risk of suicidal thoughts and behavior and advise them of the need to be alert for the emergence or worsening of symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm. Behaviors of concern should be reported immediately to healthcare providers (see WARNINGS, Suicidal Behavior and Ideation subsection). Warn patients about the possible development of hyperammonemia with or without encephalopathy. Although hyperammonemia may be asymptomatic, clinical symptoms of hyperammonemic encephalopathy often include acute alterations in level of consciousness and/or cognitive function with lethargy and/or vomiting. Instruct patients to contact their physician if they develop unexplained lethargy, vomiting, or changes in mental status (see WARNINGS, Hyperammonemia and Encephalopathy subsection). Patients should contact their physician immediately if they develop fast breathing, fatigue/tiredness, loss of appetite, or irregular heart beat or palpitations, which are possible manifestations of metabolic acidosis (see WARNINGS, Metabolic Acidosis subsection). As with other AEDs, patients should contact their physician if they intend to become pregnant or are pregnant during zonisamide therapy. Patients should notify their physician if they intend to breast-feed or are breast-feeding an infant (see PRECAUTIONS, Use in Nursing Mothers subsection). Encourage patients 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 (see PRECAUTIONS, Pregnancy subsection). In several clinical studies, zonisamide was associated with a mean increase in the concentration of serum creatinine and blood urea nitrogen (BUN) of approximately 8% over the baseline measurement. Consideration should be given to monitoring renal function periodically (see PRECAUTIONS, Effect on Renal Function subsection). Zonisamide increases serum chloride and alkaline phosphatase and decreases serum bicarbonate (see WARNINGS, Metabolic Acidosis subsection), phosphorus, calcium, and albumin. Drug Interactions with CNS Depressants: Concomitant administration of zonisamide and alcohol or other CNS depressant drugs has not been evaluated in clinical studies. Because of the potential of zonisamide to cause CNS depression, as well as other cognitive and/or neuropsychiatric adverse events, zonisamide should be used with caution if used in combination with alcohol or other CNS depressants. Other Carbonic Anhydrase Inhibitors: Concomitant use of zonisamide, a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., topiramate, acetazolamide or dichlorphenamide), may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation or the risk of hyperammonemia. Therefore, if zonisamide is given concomitantly with another carbonic anhydrase inhibitor, the patient should be monitored for the appearance or worsening of metabolic acidosis (see CLINICAL PHARMACOLOGY, Interactions of Zonisamide with Other Carbonic Anhydrase Inhibitors subsection). No evidence of carcinogenicity was found in mice or rats following dietary administration of zonisamide for two years at doses of up to 80 mg/kg/day. In mice, this dose is approximately equivalent to the maximum recommended human dose (MRHD) of 400 mg/day on a mg/m 2 basis. In rats, this dose is 1 to 2 times the MRHD on a mg/m 2 basis. Zonisamide was mutagenic in an in vitro chromosomal aberration assay in CHL cells. Zonisamide was not mutagenic or clastogenic in other in vitro assays (Ames, mouse lymphoma tk assay, chromosomal aberration in human lymphocytes) or in the in vivo rat bone marrow cytogenetics assay. Rats treated with zonisamide (20 mg, 60 mg, or 200 mg/kg) before mating and during the initial gestation phase showed signs of reproductive toxicity (decreased corpora lutea, implantations, and live fetuses) at all doses. The low dose in this study is approximately 0.5 times the maximum recommended human dose (MRHD) on a mg/m 2 basis. (see WARNINGS, Teratogenicity subsection): Zonisamide may cause serious adverse fetal effects, based on clinical and nonclinical data. Zonisamide was teratogenic in multiple animal species. Zonisamide treatment causes metabolic acidosis in humans. The effect of zonisamide-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) may be associated with decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus's ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the non-pregnant state. (See WARNINGS, Metabolic Acidosis subsection.) Newborns of mothers treated with zonisamide should be monitored for metabolic acidosis because of transfer of zonisamide to the fetus and possible occurrence of transient metabolic acidosis following birth. Transient metabolic acidosis has been reported in neonates born to mothers treated during pregnancy with a different carbonic anhydrase inhibitor. Zonisamide was teratogenic in mice, rats, and dogs and embryolethal in monkeys when administered during the period of organogenesis. Fetal abnormalities or embryo-fetal deaths occurred in these species at zonisamide dosage and maternal plasma levels similar to or lower than therapeutic levels in humans, indicating that use of this drug in pregnancy entails a significant risk to the fetus. A variety of external, visceral, and skeletal malformations was produced in animals by prenatal exposure to zonisamide. Cardiovascular defects were prominent in both rats and dogs. Following administration of zonisamide (10 mg, 30 mg, or 60 mg/kg/day) to pregnant dogs during organogenesis, increased incidences of fetal cardiovascular malformations (ventricular septal defects, cardiomegaly, various valvular and arterial anomalies) were found at doses of 30 mg/kg/day or greater. The low effect dose for malformations produced peak maternal plasma zonisamide levels (25 mcg/mL) about 0.5 times the highest plasma levels measured in patients receiving the maximum recommended human dose (MRHD) of 400 mg/day. In dogs, cardiovascular malformations were found in approximately 50% of all fetuses exposed to the high dose, which was associated with maternal plasma levels (44 mcg/mL) approximately equal to the highest levels measured in humans receiving the MRHD. Incidences of skeletal malformations were also increased at the high dose, and fetal growth retardation and increased frequencies of skeletal variations were seen at all doses in this study. The low dose produced maternal plasma levels (12 mcg/mL) about 0.25 times the highest human levels. In cynomolgus monkeys, administration of zonisamide (10 mg or 20 mg/kg/day) to pregnant animals during organogenesis resulted in embryo-fetal deaths at both doses. The possibility that these deaths were due to malformations cannot be ruled out. The lowest embryolethal dose in monkeys was associated with peak maternal plasma zonisamide levels (5 mcg/mL) approximately 0.1 times the highest levels measured in patients at the MRHD. In a mouse embryo-fetal development study, treatment of pregnant animals with zonisamide (125 mg, 250 mg, or 500 mg/kg/day) during the period of organogenesis resulted in increased incidences of fetal malformations (skeletal and/or craniofacial defects) at all doses tested. The low dose in this study is approximately 1.5 times the MRHD on a mg/m 2 basis. In rats, increased frequencies of malformations (cardiovascular defects) and variations (persistent cords of thymic tissue, decreased skeletal ossification) were observed among the offspring of dams treated with zonisamide (20 mg, 60 mg, or 200 mg/kg/day) throughout organogenesis at all doses. The low effect dose is approximately 0.5 times the MRHD on a mg/m 2 basis. Perinatal death was increased among the offspring of rats treated with zonisamide (10, 30, or 60 mg/kg/day) from the latter part of gestation up to weaning at the high dose, or approximately 1.4 times the MRHD on a mg/m 2 basis. The no effect level of 30 mg/kg/day is approximately 0.7 times the MRHD on a mg/ m 2 basis. There are no adequate and well-controlled studies in pregnant women. Zonisamide should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. To provide information regarding the effects of in utero exposure to zonisamide, physicians are advised to recommend that pregnant patients taking zonisamide enroll in the NAAED Pregnancy Registry. This can be done by calling the toll-free number 1-888-233-2334, and must be done by patients themselves. Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/ . The effect of zonisamide on labor and delivery in humans is not known. Zonisamide is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from zonisamide, a decision should be made whether to discontinue nursing or to discontinue drug, taking into account the importance of the drug to the mother. The safety and effectiveness of zonisamide in children under age 16 have not been established. Acute myopia and secondary angle closure glaucoma have been reported in pediatric patients (see WARNINGS, Acute Myopia and Secondary Angle Closure Glaucoma subsection). Cases of oligohidrosis and hyperpyrexia have been reported (see WARNINGS, Oligohidrosis and Hyperthermia in Pediatric Patients subsection). Zonisamide commonly causes metabolic acidosis in pediatric patients (see WARNINGS, Metabolic Acidosis subsection). Hyperammonemia with encephalopathy has been reported in pediatric patients (see WARNINGS, Hyperammonemia and Encephalopathy subsection). Chronic untreated metabolic acidosis in pediatric patients may cause nephrolithiasis and/or nephrocalcinosis, osteoporosis and/or osteomalacia (potentially resulting in rickets), and may reduce growth rates. A reduction in growth rate may eventually decrease the maximal height achieved. The effect of zonisamide on growth and bone-related sequelae has not been systematically investigated. Single dose pharmacokinetic parameters are similar in elderly and young healthy volunteers (see CLINICAL PHARMACOLOGY, Specific Populations subsection). Clinical studies of zonisamide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

The most common adverse reactions with zonisamide (an incidence at least 4% greater than placebo) in controlled clinical trials and shown in descending order of frequency were somnolence, anorexia, dizziness, ataxia, agitation/irritability, and difficulty with memory and/or concentration.

Drug Interactions with CNS Depressants: Concomitant administration of zonisamide and alcohol or other CNS depressant drugs has not been evaluated in clinical studies. Because of the potential of zonisamide to cause CNS depression, as well as other cognitive and/or neuropsychiatric adverse events, zonisamide should be used with caution if used in combination with alcohol or other CNS depressants. Other Carbonic Anhydrase Inhibitors: Concomitant use of zonisamide, a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., topiramate, acetazolamide or dichlorphenamide), may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation or the risk of hyperammonemia. Therefore, if zonisamide is given concomitantly with another carbonic anhydrase inhibitor, the patient should be monitored for the appearance or worsening of metabolic acidosis (see CLINICAL PHARMACOLOGY, Interactions of Zonisamide with Other Carbonic Anhydrase Inhibitors subsection).

Zonisamide, USP is available as 100 mg two-piece hard gelatin capsules. The capsules imprinted with codes are printed in black ink. Zonisamide, USP is available in unit dose packages with strengths and capsule description as follows: Dosage Strength Capsule Description NDC# 100 mg Unit Dose Packages of 100 (10 x 10) Size "1" Brown Opaque Cap and White Opaque Body imprinted with 100 mg on the cap and IG228 on the body in black ink, filled with White to Off-white powder. 60687-230-01 Store at 20°C to 25°C (68°F to 77°F) [see USP Controlled Room Temperature], in a dry place and protected from light. FOR YOUR PROTECTION: Do not use if blister is torn or broken.

The precise mechanism(s) by which zonisamide exerts its antiseizure effect is unknown. Zonisamide demonstrated anticonvulsant activity in several experimental models. In animals, zonisamide was effective against tonic extension seizures induced by maximal electroshock but ineffective against clonic seizures induced by subcutaneous pentylenetetrazol. Zonisamide raised the threshold for generalized seizures in the kindled rat model and reduced the duration of cortical focal seizures induced by electrical stimulation of the visual cortex in cats. Furthermore, zonisamide suppressed both interictal spikes and the secondarily generalized seizures produced by cortical application of tungstic acid gel in rats or by cortical freezing in cats. The relevance of these models to human epilepsy is unknown. Zonisamide may produce these effects through action at sodium and calcium channels. In vitro pharmacological studies suggest that zonisamide blocks sodium channels and reduces voltage-dependent, transient inward currents (T-type Ca 2+ currents), consequently stabilizing neuronal membranes and suppressing neuronal hypersynchronization. In vitro binding studies have demonstrated that zonisamide binds to the GABA/benzodiazepine receptor ionophore complex in an allosteric fashion which does not produce changes in chloride flux. Other in vitro studies have demonstrated that zonisamide (10 to 30 mcg/mL) suppresses synaptically-driven electrical activity without affecting postsynaptic GABA or glutamate responses (cultured mouse spinal cord neurons) or neuronal or glial uptake of [ 3 H]-GABA (rat hippocampal slices). Thus, zonisamide does not appear to potentiate the synaptic activity of GABA. In vivo microdialysis studies demonstrated that zonisamide facilitates both dopaminergic and serotonergic neurotransmission. Zonisamide is a carbonic anhydrase inhibitor. The contribution of this pharmacological action to the therapeutic effects of zonisamide is unknown. However, as a carbonic anhydrase inhibitor, zonisamide may cause metabolic acidosis (see WARNINGS, Metabolic Acidosis subsection). Absorption Following a 200 to 400 mg oral zonisamide dose, peak plasma concentrations (range: 2 to 5 mcg/mL) in normal volunteers occur within 2 to 6 hours. In the presence of food, the time to maximum concentration is delayed, occurring at 4 to 6 hours, but food has no effect on the bioavailability of zonisamide. Zonisamide absorption is dose proportional in the range of 200 to 400 mg. C max and AUC, however, increase disproportionately at 800 mg, possibly due to saturable binding of zonisamide to red blood cells. Once a stable dose is reached, steady state is achieved within 14 days. Distribution The apparent volume of distribution (V/F) of zonisamide is about 1.45 L/kg following a 400 mg oral dose. Zonisamide, at concentrations of 1.0 to 7.0 mcg/mL, is approximately 40% bound to human plasma proteins. Zonisamide extensively binds to erythrocytes, resulting in an eight-fold higher concentration of zonisamide in red blood cells than in plasma. Protein binding of zonisamide is unaffected in the presence of therapeutic concentrations of phenytoin, phenobarbital or carbamazepine. Metabolism and Elimination: ollowing oral administration of 14 C-zonisamide to healthy volunteers, only zonisamide was detected in plasma. Zonisamide is excreted primarily in urine as parent drug and as the glucuronide of a metabolite. Following multiple dosing, 62% of the radiolabeled dose was recovered in the urine, with 3% in the feces by day 10. Zonisamide undergoes acetylation by N-acetyl-transferases to form N-acetyl zonisamide and reduction to form the open ring metabolite, 2–sulfamoylacetyl phenol (SMAP). Of the excreted dose, 35% was recovered as zonisamide, 15% as N-acetyl zonisamide, and 50% as the glucuronide of SMAP. Reduction of zonisamide to SMAP is mediated by cytochrome P450 isozyme 3A4 (CYP3A4). Zonisamide does not induce its own metabolism. The plasma clearance of oral zonisamide is approximately 0.30 to 0.35 mL/min/kg in patients not receiving enzyme-inducing antiepilepsy drugs (AEDs). The clearance of zonisamide is increased to 0.5 mL/min/kg in patients concurrently on enzyme-inducing AEDs. After a single-dose administration, renal clearance of zonisamide is approximately 3.5 mL/min. The clearance of an oral dose of zonisamide from red blood cells is 2 mL/min. The elimination half-life of zonisamide in plasma is approximately 63 hours. The elimination half-life of zonisamide in red blood cells is approximately 105 hours. Renal Impairment: Single 300 mg zonisamide doses were administered to three groups of volunteers. Group 1 was a healthy group with a creatinine clearance ranging from 70 to 152 mL/min. Group 2 and Group 3 had creatinine clearances ranging from 14.5 to 59 mL/min and 10 to 20 mL/min, respectively. Zonisamide renal clearance decreased with decreasing renal function (3.42, 2.50, 2.23 mL/min, respectively). Marked renal impairment (creatinine clearance < 20 mL/min) was associated with an increase in zonisamide AUC of 35% (see DOSAGE AND ADMINISTRATION section). Hepatic Impairment: The pharmacokinetics of zonisamide in patients with impaired liver function have not been studied (see DOSAGE AND ADMINISTRATION section). Age: The pharmacokinetics of a 300 mg single dose of zonisamide was similar in young (mean age 28 years) and elderly subjects (mean age 69 years). Gender and Race: Information on the effect of gender and race on the pharmacokinetics of zonisamide is not available. In vitro studies using human liver microsomes show insignificant (<25%) inhibition of cytochrome P450 isozymes 1A2, 2A6, 2C9, 2C19, 2D6, 2E1, 3A4, 2B6 or 2C8 at zonisamide levels approximately two-fold or greater than clinically relevant unbound serum concentrations. Therefore, Zonisamide is not expected to affect the pharmacokinetics of other drugs via cytochrome P450-mediated mechanisms. Anti-epileptic drugs In epileptic patients, steady-state dosing with Zonisamide resulted in no clinically relevant pharmacokinetic effects on carbamazepine, lamotrigine, phenytoin, or sodium valproate. Oral contraceptives In healthy subjects, steady state dosing with Zonisamide did not affect serum concentrations of ethinylestradiol or norethisterone in a combined oral contraceptive. CYP2D6 substrates Coadministration of multiple dosing of zonisamide up to 400 mg/day with single 50-mg doses of desipramine did not significantly affect the pharmacokinetic parameters of desipramine, a probe drug for CYP2D6 activity. P-gp substrate An in vitro study showed that zonisamide is a weak inhibitor of P-gp (MDR1) with an IC 50 of 267 µmol/L. There is a theoretical potential for zonisamide to affect the pharmacokinetics of drugs which are P-gp substrates. Caution is advised when starting or stopping Zonisamide or changing the Zonisamide dose in patients who are also receiving drugs which are P-gp substrates (e.g., digoxin, quinidine). Concomitant medications that can induce or inhibit CYP3A4 or N-acetyl-transferases may affect the pharmacokinetics of zonisamide. Drugs which inhibit or induce glucuronide conjugation are not expected to influence the pharmacokinetics of zonisamide. The absence of a clinically significant pharmacokinetic interaction between zonisamide and lamotrigine indicates a low potential for zonisamide to interact with substances which are metabolized by UDP-GT. CYP3A4 Induction : Drugs that induce liver enzymes increase the metabolism and clearance of zonisamide and decrease its half-life. The half-life of zonisamide following a 400 mg dose in patients concurrently on enzyme-inducing AEDs such as phenytoin, carbamazepine, or phenobarbital was between 27 to 38 hours, the half-life of zonisamide in patients concurrently on the non-enzyme inducing AED, valproate, was 46 hours. These effects are unlikely to be of clinical significance when Zonisamide is added to existing therapy; however, changes in zonisamide concentrations may occur if concomitant CYP3A4 inducing anti-epileptic or other drugs are withdrawn, dose adjusted or introduced, an adjustment of the Zonisamide dose may be required. If co-administration with a potent CYP3A4 inducer (e.g., rifampicin) is necessary, the patient should be closely monitored and the dose of Zonisamide and other drugs that are CYP3A4 substrate may need to be adjusted. CYP3A4 Inhibition: Steady-state dosing of either ketoconazole (400 mg/day) or cimetidine (1200 mg/day) had no clinically relevant effects on the single dose pharmacokinetics of zonisamide given to healthy subjects. Therefore, modification of Zonisamide dosing is not necessary when co-administered with known CYP3A4 inhibitors. Concomitant use of zonisamide a carbonic anhydrase inhibitor, with any other carbonic anhydrase inhibitor (e.g., topiramate, acetazolamide or dichlorphenamide), may increase the severity of metabolic acidosis and may also increase the risks of hyperammonemia and kidney stone formation. Therefore, if zonisamide is given concomitantly with another carbonic anhydrase inhibitor, the patient should be monitored for the appearance or worsening of metabolic acidosis (see WARNINGS, Metabolic Acidosis subsection and Hyperammonemia and Encephalopathy subsection and PRECAUTIONS, Drug Interactions subsection). The effectiveness of zonisamide as adjunctive therapy (added to other antiepilepsy drugs) has been established in three multicenter, placebo-controlled, double blind, 3-month clinical trials (two domestic, one European) in 499 patients with refractory partial onset seizures with or without secondary generalization. Each patient had a history of at least four partial onset seizures per month in spite of receiving one or two antiepilepsy drugs at therapeutic concentrations. The 499 patients (209 women, 290 men) ranged in age from 13 to 68 years with a mean age of about 35 years. In the two US studies, over 80% of patients were Caucasian; 100% of patients in the European study were Caucasian. Zonisamide or placebo was added to the existing therapy. The primary measure of effectiveness was median percent reduction from baseline in partial seizure frequency. The secondary measure was proportion of patients achieving a 50% or greater seizure reduction from baseline (responders). The results described below are for all partial seizures in the intent-to-treat populations. In the first study (n = 203), all patients had a 1-month baseline observation period, then received placebo or zonisamide in one of two dose escalation regimens; either 1) 100 mg/day for five weeks, 200 mg/day for one week, 300 mg/day for one week, and then 400 mg/day for five weeks; or 2) 100 mg/day for one week, followed by 200 mg/day for five weeks, then 300 mg/day for one week, then 400 mg/day for five weeks. This design allowed a 100 mg vs. placebo comparison over weeks 1 to 5, and a 200 mg vs. placebo comparison over weeks 2 to 6; the primary comparison was 400 mg (both escalation groups combined) vs. placebo over weeks 8 to 12. The total daily dose was given as twice a day dosing. Statistically significant treatment differences favoring zonisamide were seen for doses of 100, 200, and 400 mg/day. In the second (n = 152) and third (n = 138) studies, patients had a 2 to 3 month baseline, then were randomly assigned to placebo or zonisamide for three months. Zonisamide was introduced by administering 100 mg/day for the first week, 200 mg/day the second week, then 400 mg/day for two weeks, after which the dose (zonisamide or placebo) could be adjusted as necessary to a maximum dose of 20 mg/kg/day or a maximum plasma level of 40 mcg/mL. In the second study, the total daily dose was given as twice a day dosing; in the third study, it was given as a single daily dose. The average final maintenance doses received in the studies were 530 and 430 mg/day in the second and third studies, respectively. Both studies demonstrated statistically significant differences favoring zonisamide for doses of 400 to 600 mg/day, and there was no apparent difference between once daily and twice daily dosing (in different studies). Analysis of the data (first 4 weeks) during titration demonstrated statistically significant differences favoring zonisamide at doses between 100 and 400 mg/day. The primary comparison in both trials was for any dose over Weeks 5 to 12. Table 1. Median % Reduction in All Partial Seizures and % Responders in Primary Efficacy Analyses: Intent-To-Treat Analysis Study Median % Reduction in Partial Seizures % Responders Zonisamide Placebo Zonisamide Placebo Study 1 n=98 n=72 n=98 n=72 Weeks 8-12 40.5% p<0.05 compared to placebo 9.0% 41.8% 22.2% Study 2 n=69 n=72 n=69 n=72 Weeks 5-12 29.6% -3.2% 29.0% 15.0% Study 3 n=67 n=66 n=67 n=66 Weeks 5-12 27.2% -1.1% 28.0% 12.0% Table 2. Median % Reduction in All Partial Seizures and % Responders for Dose Analyses in Study 1: Intent-To-Treat Analysis Dose Group Median % Reduction in Partial Seizures % Responders Zonisamide Placebo Zonisamide Placebo 100 to 400 mg/day n=112 n=83 n=112 n=83 Weeks 1 to 12 32.3% p<0.05 compared to placebo 5.6% 32.1% 9.6% 100 mg/day n=56 n=80 n=56 n=80 Weeks 1 to 5 24.7% 8.3% 25.0% 11.3% 200 mg/day n=55 n=82 n=55 n=82 Weeks 2 to 6 20.4% 4.0% 25.5% 9.8% Figure 1 presents the proportion of patients (X-axis) whose percentage reduction from baseline in the all partial seizure rate was at least as great as that indicated on the Y-axis in the second and third placebo-controlled trials. A positive value on the Y-axis indicates an improvement from baseline (i.e., a decrease in seizure rate), while a negative value indicates a worsening from baseline (i.e., an increase in seizure rate). Thus, in a display of this type, the curve for an effective treatment is shifted to the left of the curve for placebo. The proportion of patients achieving any particular level of reduction in seizure rate was consistently higher for the zonisamide groups compared to the placebo groups. For example, Figure 1 indicates that approximately 27% of patients treated with zonisamide experienced a 75% or greater reduction, compared to approximately 12% in the placebo groups. Figure 1 Proportion of Patients Achieving Differing Levels of Seizure Reduction in Zonisamide and Placebo Groups in Studies 2 and 3 No differences in efficacy based on age, sex or race, as measured by a change in seizure frequency from baseline, were detected. Figure 1 Proportion of Patients Achieving Differing Levels of Seizure Reduction in Zonisamide and Placebo Groups in Studies 2 and 3

The effectiveness of zonisamide as adjunctive therapy (added to other antiepilepsy drugs) has been established in three multicenter, placebo-controlled, double blind, 3-month clinical trials (two domestic, one European) in 499 patients with refractory partial onset seizures with or without secondary generalization. Each patient had a history of at least four partial onset seizures per month in spite of receiving one or two antiepilepsy drugs at therapeutic concentrations. The 499 patients (209 women, 290 men) ranged in age from 13 to 68 years with a mean age of about 35 years. In the two US studies, over 80% of patients were Caucasian; 100% of patients in the European study were Caucasian. Zonisamide or placebo was added to the existing therapy. The primary measure of effectiveness was median percent reduction from baseline in partial seizure frequency. The secondary measure was proportion of patients achieving a 50% or greater seizure reduction from baseline (responders). The results described below are for all partial seizures in the intent-to-treat populations. In the first study (n = 203), all patients had a 1-month baseline observation period, then received placebo or zonisamide in one of two dose escalation regimens; either 1) 100 mg/day for five weeks, 200 mg/day for one week, 300 mg/day for one week, and then 400 mg/day for five weeks; or 2) 100 mg/day for one week, followed by 200 mg/day for five weeks, then 300 mg/day for one week, then 400 mg/day for five weeks. This design allowed a 100 mg vs. placebo comparison over weeks 1 to 5, and a 200 mg vs. placebo comparison over weeks 2 to 6; the primary comparison was 400 mg (both escalation groups combined) vs. placebo over weeks 8 to 12. The total daily dose was given as twice a day dosing. Statistically significant treatment differences favoring zonisamide were seen for doses of 100, 200, and 400 mg/day. In the second (n = 152) and third (n = 138) studies, patients had a 2 to 3 month baseline, then were randomly assigned to placebo or zonisamide for three months. Zonisamide was introduced by administering 100 mg/day for the first week, 200 mg/day the second week, then 400 mg/day for two weeks, after which the dose (zonisamide or placebo) could be adjusted as necessary to a maximum dose of 20 mg/kg/day or a maximum plasma level of 40 mcg/mL. In the second study, the total daily dose was given as twice a day dosing; in the third study, it was given as a single daily dose. The average final maintenance doses received in the studies were 530 and 430 mg/day in the second and third studies, respectively. Both studies demonstrated statistically significant differences favoring zonisamide for doses of 400 to 600 mg/day, and there was no apparent difference between once daily and twice daily dosing (in different studies). Analysis of the data (first 4 weeks) during titration demonstrated statistically significant differences favoring zonisamide at doses between 100 and 400 mg/day. The primary comparison in both trials was for any dose over Weeks 5 to 12. Table 1. Median % Reduction in All Partial Seizures and % Responders in Primary Efficacy Analyses: Intent-To-Treat Analysis Study Median % Reduction in Partial Seizures % Responders Zonisamide Placebo Zonisamide Placebo Study 1 n=98 n=72 n=98 n=72 Weeks 8-12 40.5% p<0.05 compared to placebo 9.0% 41.8% 22.2% Study 2 n=69 n=72 n=69 n=72 Weeks 5-12 29.6% -3.2% 29.0% 15.0% Study 3 n=67 n=66 n=67 n=66 Weeks 5-12 27.2% -1.1% 28.0% 12.0% Table 2. Median % Reduction in All Partial Seizures and % Responders for Dose Analyses in Study 1: Intent-To-Treat Analysis Dose Group Median % Reduction in Partial Seizures % Responders Zonisamide Placebo Zonisamide Placebo 100 to 400 mg/day n=112 n=83 n=112 n=83 Weeks 1 to 12 32.3% p<0.05 compared to placebo 5.6% 32.1% 9.6% 100 mg/day n=56 n=80 n=56 n=80 Weeks 1 to 5 24.7% 8.3% 25.0% 11.3% 200 mg/day n=55 n=82 n=55 n=82 Weeks 2 to 6 20.4% 4.0% 25.5% 9.8% Figure 1 presents the proportion of patients (X-axis) whose percentage reduction from baseline in the all partial seizure rate was at least as great as that indicated on the Y-axis in the second and third placebo-controlled trials. A positive value on the Y-axis indicates an improvement from baseline (i.e., a decrease in seizure rate), while a negative value indicates a worsening from baseline (i.e., an increase in seizure rate). Thus, in a display of this type, the curve for an effective treatment is shifted to the left of the curve for placebo. The proportion of patients achieving any particular level of reduction in seizure rate was consistently higher for the zonisamide groups compared to the placebo groups. For example, Figure 1 indicates that approximately 27% of patients treated with zonisamide experienced a 75% or greater reduction, compared to approximately 12% in the placebo groups. Figure 1 Proportion of Patients Achieving Differing Levels of Seizure Reduction in Zonisamide and Placebo Groups in Studies 2 and 3 No differences in efficacy based on age, sex or race, as measured by a change in seizure frequency from baseline, were detected. Figure 1 Proportion of Patients Achieving Differing Levels of Seizure Reduction in Zonisamide and Placebo Groups in Studies 2 and 3

NDC 60687- 230 -01 Zonisamide Capsules, USP 100 mg 100 Capsules (10 x 10)                 Rx Only PHARMACIST: Dispense with Medication Guide to each patient. Each Capsule Contains: Zonisamide USP....................................................................100 mg Usual Dosage: See full prescribing information. Store at 20° to 25°C (68° to 77°F) in a dry place and protected from light; excursions permitted between 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature]. FOR YOUR PROTECTION: Do not use if blister is torn or broken. The drug product contained in this package is from NDC # 69097-861, Cipla USA, Inc. Distributed by: American Health Packaging, Columbus, Ohio 43217 723001 0423001/1123 100 mg Zonisamide Carton