Vigabatrin

VIGAFYDE is indicated as monotherapy for the treatment of i nfantile spasms in pediatric patients 1 month to 2 years of age for whom the potential benefits outweigh the potential risk of vision loss. ( 1 ) VIGAFYDE is indicated as monotherapy for the treatment of infantile spasms in pediatric patients 1 month to 2 years of age for whom the potential benefits outweigh the potential risk of vision loss [see Warnings and Precautions ( 5.1 )].

Oral Solution : 100 mg/mL clear, colorless to light yellow solution with a peppermint odor. Oral Solution : 100 mg/mL ( 3 )

None. None ( 4 )

Abnormal MRI signal changes and intramyelinic edema have been reported in some infants with infantile spasms receiving VIGAFYDE. ( 5.3 , 5.4 ) Withdrawal of AEDs: Taper dose to avoid withdrawal seizures. ( 5.5 ) Anemia: Monitor for symptoms of anemia. ( 5.6 )

5.1 Permanent Vision Loss VIGAFYDE can cause permanent vision loss. Because of this risk and because, when it is effective, VIGAFYDE provides an observable symptomatic benefit; patient response and continued need for treatment should be periodically assessed. VIGAFYDE is indicated for treatment in patients 1 month to 2 years of age [see Indications and Usage ( 1 )]. VIGAFYDE is not approved for use in pediatric patients older than 2 years of age or in adults. Based upon adult studies, 30 percent or more of patients can be affected with bilateral concentric visual field constriction ranging in severity from mild to severe. Severe cases may be characterized by tunnel vision to within 10 degrees of visual fixation, which can result in disability. In some cases, VIGAFYDE also can damage the central retina and may decrease visual acuity. Symptoms of vision loss from VIGAFYDE are unlikely to be recognized by patients or caregivers before vision loss is severe. Vision loss of milder severity, while often unrecognized by the patient or caregiver, can still adversely affect function. Because assessing vision may be difficult in infants and children, the frequency and extent of vision loss is poorly characterized in these patients. For this reason, the understanding of the risk is primarily based on the adult experience. The possibility that vision loss from VIGAFYDE may be more common, more severe, or have more severe functional consequences in infants than in adults cannot be excluded. The onset of vision loss from VIGAFYDE is unpredictable and can occur within weeks of starting treatment or sooner, or at any time after starting treatment, even after months or years. The risk of vision loss increases with increasing dose and cumulative exposure, but there is no dose or exposure known to be free of risk of vision loss. In patients with infantile spasms, VIGAFYDE should be withdrawn if a substantial clinical benefit is not observed within 2 to 4 weeks. If, in the clinical judgment of the prescriber, evidence of treatment failure becomes obvious earlier than 2 to 4 weeks, treatment should be discontinued at that time [see Dosage and Administration ( 2.2 ) and Warnings and Precautions ( 5.5 )]. VIGAFYDE should not be used in patients with, or at high risk of, other types of irreversible vision loss unless the benefits of treatment clearly outweigh the risks. The interaction of other types of irreversible vision damage with vision damage from VIGAFYDE has not been well-characterized, but is likely adverse. VIGAFYDE should not be used with other drugs associated with serious adverse ophthalmic effects such as retinopathy or glaucoma unless the benefits clearly outweigh the risks. Monitoring of Vision Monitoring of vision by an ophthalmic professional with expertise in visual field interpretation and the ability to perform dilated indirect ophthalmoscopy of the retina is recommended [see Warnings and Precautions ( 5.2 )]. Because vision testing in infants is difficult, vision loss may not be detected until it is severe. For patients receiving VIGAFYDE, vision assessment is recommended at baseline (no later than 4 weeks after starting VIGAFYDE), at least every 3 months while on therapy, and about 3 to 6 months after the discontinuation of therapy. The diagnostic approach should be individualized for the patient and clinical situation. In cooperative pediatric patients, perimetry is recommended, preferably by automated threshold visual field testing. Additional testing may also include electrophysiology (e.g., electroretinography [ERG]), retinal imaging (e.g., optical coherence tomography [OCT]), and/or other methods appropriate for the patient. In patients who cannot be tested, treatment may continue according to clinical judgment, with appropriate caregiver counseling. Because of variability, results from ophthalmic monitoring must be interpreted with caution, and repeat assessment is recommended if results are abnormal or uninterpretable. Repeat assessment in the first few weeks of treatment is recommended to establish if, and to what degree, reproducible results can be obtained, and to guide selection of appropriate ongoing monitoring for the patient. The onset and progression of vision loss from VIGAFYDE is unpredictable, and it may occur or worsen precipitously between assessments. Once detected, vision loss due to VIGAFYDE is not reversible. It is expected that even with frequent monitoring, some VIGAFYDE patients will develop severe vision loss. Consider drug discontinuation, balancing benefit and risk, if vision loss is documented. It is possible that vision loss can worsen despite discontinuation of VIGAFYDE.

5.2 Vigabatrin REMS VIGAFYDE is available only through a restricted distribution program called the Vigabatrin REMS, because of the risk of permanent vision loss. Notable requirements of the Vigabatrin REMS include the following: Prescribers must be certified by enrolling in the program, agreeing to counsel caregivers on the risk of vision loss and the need for periodic monitoring of vision, and reporting any event suggestive of vision loss to the REMS program. Patients must enroll in the program. Pharmacies must be certified and must only dispense to patients authorized to receive VIGAFYDE. Further information is available at www.vigabatrinREMS.com or by calling 1-866-244-8175.

5.3 Magnetic Resonance Imaging Abnormalities in Infants Abnormal magnetic resonance imaging (MRI) signal changes characterized by increased T2 signal and restricted diffusion in a symmetric pattern involving the thalamus, basal ganglia, brain stem, and cerebellum have been observed in some infants treated with vigabatrin. In a retrospective epidemiologic study in infants with infantile spasms (N=205), the prevalence of MRI changes was 22% in vigabatrin-treated patients versus 4% in patients treated with other therapies. In this study, in postmarketing experience, and in published literature reports, these changes generally resolved with discontinuation of treatment. In a few patients, the lesion resolved despite continued use. It has been reported that some infants exhibited coincident motor abnormalities, but no causal relationship has been established and the potential for long-term clinical sequelae has not been adequately studied. Neurotoxicity (brain histopathology and neurobehavioral abnormalities) was observed in rats exposed to vigabatrin during late gestation and the neonatal and juvenile periods of development, and brain histopathological changes were observed in dogs exposed to vigabatrin during the juvenile period of development. The relationship between these findings and the abnormal MRI findings in infants treated with vigabatrin for infantile spasms is unknown [see Warnings and Precautions ( 5.4 ) and Use in Specific Populations ( 8.1 )] .

5.4 Neurotoxicity Intramyelinic Edema (IME) has been reported in postmortem examination of infants being treated for infantile spasms with vigabatrin. Abnormal MRI signal changes characterized by increased T2 signal and restricted diffusion in a symmetric pattern involving the thalamus, basal ganglia, brain stem, and cerebellum have also been observed in some infants treated for IS with vigabatrin [see Warnings and Precautions ( 5.3 )] . Vacuolation, characterized by fluid accumulation and separation of the outer layers of myelin, has been observed in brain white matter tracts in adult and juvenile rats and adult mice, dogs, and possibly monkeys following administration of vigabatrin. This lesion, referred to as intramyelinic edema (IME), was seen in animals at doses within the human therapeutic range. A no-effect dose was not established in rodents or dogs. […]

The following serious and otherwise important adverse reactions are described elsewhere in labeling: Permanent Vision Loss [see BOXED WARNING and Warnings and Precautions ( 5.1 )] Magnetic Resonance Imaging (MRI) Abnormalities in Infants [see Warnings and Precautions ( 5.3 )] Neurotoxicity [see Warnings and Precautions ( 5.4 )] Withdrawal of Antiepileptic Drugs (AEDs) [see Warnings and Precautions ( 5.5 )] Anemia [see Warnings and Precautions ( 5.6 )] Somnolence and Fatigue [see Warnings and Precautions ( 5.7 )] Peripheral Neuropathy [see Warnings and Precautions ( 5.8 )] Weight Gain [see Warnings and Precautions ( 5.9 )] Edema [see Warnings and Precautions ( 5.10 )] Suicidal Behavior and Ideation with Unapproved use in Adolescents and Adults [see Warnings and Precautions ( 5.11 )] The most common adverse reactions (incidence ˃5% and greater than on placebo) in patients with infantile spasms include somnolence, bronchitis, ear infection, and acute otitis media. ( 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 Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Infantile Spasms In a randomized, placebo-controlled study in patients with infantile spasms (IS) with a 5 day double-blind treatment phase (n=40), the adverse reactions that occurred in ≥5% of patients receiving vigabatrin and that occurred more frequently than in placebo patients were somnolence (vigabatrin 45%, placebo 30%), bronchitis (vigabatrin 30%, placebo 15%), ear infection (vigabatrin 10%, placebo 5%), and acute otitis media (vigabatrin 10%, placebo 0%). In patients with IS, the adverse reactions most commonly associated with vigabatrin treatment discontinuation in ≥1% of patients were infections, status epilepticus, developmental coordination disorder, dystonia, hypotonia, hypertonia, weight gain, and insomnia. In a dose response study of low-dose (18 to 36 mg/kg/day, which is below the recommended starting dose for IS of 50 mg/kg/day) versus high-dose (100 to 148 mg/kg/day) vigabatrin, no clear correlation between dose and incidence of adverse reactions was observed. The adverse reactions (≥5% in either dose group) are summarized in Table 2. Table 2. Adverse Reactions in a Placebo-Controlled Trial in Patients with Infantile Spasms Body System Adverse Reaction Vigabatrin Low Dose [N=114] % Vigabatrin High Dose [N=108] % Eye Disorders (other than field or acuity changes) Strabismus 5 5 Conjunctivitis 5 2 Gastrointestinal Disorders Vomiting 14 20 Constipation 14 12 Diarrhea 13 12 General Disorders Fever 29 19 Infections Upper respiratory tract infection 51 46 Otitis media 44 30 Viral infection 20 19 Pneumonia 13 11 Candidiasis 8 3 Ear infection 7 14 Gastroenteritis viral 6 5 Sinusitis 5 9 Urinary tract infection 5 6 Influenza 5 3 Croup infectious 5 1 Metabolism & Nutrition Disorders Decreased appetite 9 7 Nervous System Disorders Sedation 19 17 Somnolence 17 19 Status epilepticus 6 4 Lethargy 5 7 Convulsion 4 7 Hypotonia 4 6 Psychiatric Disorders Irritability 16 23 Insomnia 10 12 Re s piratory Disorders Nasal congestion 13 4 Cough 3 8 Skin and Subcutaneous Tissue Disorders Rash 8 11

6.2 Postm arketing Experience The following adverse reactions have been identified during postapproval use of vigabatrin. 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. Ear Disorders : Deafness Endocrine Disorders : Delayed puberty Gastrointestinal Disorders : Gastrointestinal hemorrhage, esophagitis General Disorders : Developmental delay, facial edema, malignant hyperthermia, multi-organ failure Hepatobiliary Disorders : Cholestasis Nervous System Disorders : Dystonia, encephalopathy, hypertonia, hypotonia, muscle spasticity, myoclonus, optic neuritis, dyskinesia Psychiatric Disorders : Acute psychosis, apathy, delirium, hypomania, neonatal agitation, psychotic disorder Respiratory Disorders : Laryngeal edema, pulmonary embolism, respiratory failure, stridor Skin and Subcutaneous Tissue Disorders : Angioedema, maculo-papular rash, pruritus, Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), alopecia

Decreased phenytoin plasma levels: Dosage adjustment may be needed. ( 7.1 )

7.1 Antiepileptic Drugs Phenytoin Although phenytoin dose adjustments are not routinely required, dose adjustment of phenytoin should be considered if clinically indicated, since VIGAFYDE may cause a moderate reduction in total phenytoin plasma levels [see Clinical Pharmacology ( 12.3 )]. Clonazepam VIGAFYDE may moderately increase the C max of clonazepam resulting in an increase of clonazepam-associated adverse reactions [see Clinical Pharmacology ( 12.3 )].

7.2 Drug-Laboratory Test Interactions VIGAFYDE decreases alanine transaminase (ALT) and aspartate transaminase (AST) plasma activity in up to 90% of patients. In some patients, these enzymes become undetectable. The suppression of ALT and AST activity by vigabatrin may preclude the use of these markers, especially ALT, to detect early hepatic injury. VIGAFYDE may increase the amount of amino acids in the urine, possibly leading to a false positive test for certain rare genetic metabolic diseases (e.g., alpha aminoadipic aciduria).

8.1 Pregnancy VIGAFYDE is indicated for treatment in patients 1 month to 2 years of age [see Indications and Usage ( 1 )]. VIGAFYDE is not approved for use in adolescents and adults. Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AEDs, including VIGAFYDE, during pregnancy. Encourage women who are taking VIGAFYDE during pregnancy to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll-free number 1-888-233-2334 or visiting the website, http://www.aedpregnancyregistry.org/ . This must be done by the patient herself. Risk Summary There are no adequate data on the developmental risk associated with the use of VIGAFYDE in pregnant women. Limited available data from case reports and cohort studies pertaining to vigabatrin use in pregnant women have not established a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. However, based on animal data, VIGAFYDE use in pregnant women may result in fetal harm. When administered to pregnant animals, vigabatrin produced developmental toxicity, including an increase in fetal malformations and offspring neurobehavioral and neurohistopathological effects, at clinically relevant doses. In addition, developmental neurotoxicity was observed in rats treated with vigabatrin during a period of postnatal development corresponding to the third trimester of human pregnancy ( see Data ). In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown. Data Animal Data Administration of vigabatrin (oral doses of 50 to 200 mg/kg/day) to pregnant rabbits throughout the period of organogenesis was associated with an increased incidence of malformations (cleft palate) and embryofetal death; these findings were observed in two separate studies. The no-effect dose for adverse effects on embryofetal development in rabbits (100 mg/kg/day) is approximately 1/2 the maximum recommended human dose (MRHD) of 3 g/day on a body surface area (mg/m 2 ) basis. In rats, oral administration of vigabatrin (50, 100, or 150 mg/kg/day) throughout organogenesis resulted in decreased fetal body weights and increased incidences of fetal anatomic variations. The no-effect dose for adverse effects on embryo-fetal development in rats (50 mg/kg/day) is approximately 1/5 the MRHD on a mg/m 2 basis. Oral administration of vigabatrin (50, 100, 150 mg/kg/day) to rats from the latter part of pregnancy through weaning produced long-term neurohistopathological (hippocampal vacuolation) and neurobehavioral (convulsions) abnormalities in the offspring. A no-effect dose for developmental neurotoxicity in rats was not established; the low-effect dose (50 mg/kg/day) is approximately 1/5 the MRHD on a mg/m 2 basis. In a published study, vigabatrin (300 or 450 mg/kg) was administered by intraperitoneal injection to a mutant mouse strain on a single day during organogenesis (day 7, 8, 9, 10, 11, or 12). An increase in fetal malformations (including cleft palate) was observed at both doses. Oral administration of vigabatrin (5, 15, or 50 mg/kg/day) to young rats during the neonatal and juvenile periods of development (postnatal days 4 to 65) produced neurobehavioral (convulsions, neuromotor impairment, learning deficits) and neurohistopathological (brain vacuolation, decreased myelination, and retinal dysplasia) abnormalities in treated animals. The early postnatal period in rats is generally thought to correspond to late pregnancy in humans in terms of brain development. The no-effect dose for developmental neurotoxicity in juvenile rats (5 mg/kg/day) was associated with plasma vigabatrin exposures (AUC) less than 1/30 of those measured in pediatric patients receiving an oral dose of 50 mg/kg.

8.2 Lactation VIGAFYDE is indicated for treatment in patients 1 month to 2 years of age [see Indications and Usage ( 1 )]. VIGAFYDE is not approved for use in adolescents and adults. Risk Summary Vigabatrin is excreted in human milk. The effects of vigabatrin on the breastfed infant and on milk production are unknown. Because of the potential for serious adverse reactions from vigabatrin in nursing infants, breastfeeding is not recommended. If exposing a breastfed infant to VIGAFYDE, observe for any potential adverse effects [see Warnings and Precautions ( 5.1, 5.3, 5.4, 5.8 )].

8.4 Pediatric Use The safety and effectiveness of vigabatrin as monotherapy for pediatric patients with infantile spasms (1 month to 2 years of age) have been established [see Dosage and Administration ( 2.2 ) and Clinical Studies ( 14.1 )]. Safety and effectiveness as a monotherapy for the treatment of infantile spasms in pediatric patients below the age of 1 month have not been established. Duration of therapy for infantile spasms was evaluated in a post hoc analysis of a Canadian Pediatric Epilepsy Network (CPEN) study of developmental outcomes in infantile spasms patients. This analysis suggests that a total duration of 6 months of vigabatrin therapy is adequate for the treatment of infantile spasms. However, prescribers must use their clinical judgment as to the most appropriate duration of use [see Clinical Studies ( 14.1 )]. Abnormal MRI signal changes and Intramyelinic Edema (IME) in infants and young children being treated with vigabatrin have been observed [see Warnings and Precautions ( 5.3, 5.4 )]. Juvenile Animal Toxicity Data Oral administration of vigabatrin (5, 15, or 50 mg/kg/day) to young rats during the neonatal and juvenile periods of development (postnatal days 4 to 65) produced neurobehavioral (convulsions, neuromotor impairment, learning deficits) and neurohistopathological (brain gray matter vacuolation, decreased myelination, and retinal dysplasia) abnormalities. The no-effect dose for developmental neurotoxicity in juvenile rats (the lowest dose tested) was associated with plasma vigabatrin exposures (AUC) substantially less than those measured in pediatric patients at recommended doses. In dogs, oral administration of vigabatrin (30 or 100 mg/kg/day) during selected periods of juvenile development (postnatal days 22 to 112) produced neurohistopathological abnormalities (brain gray matter vacuolation). Neurobehavioral effects of vigabatrin were not assessed in the juvenile dog. A no-effect dose for neurohistopathology was not established in juvenile dogs; the lowest effect dose (30 mg/kg/day) was associated with plasma vigabatrin exposures lower than those measured in pediatric patients at recommended doses [see Warnings and Precautions ( 5.4 )].

8.5 Geriatric Use VIGAFYDE is indicated for treatment in patients 1 month to 2 years of age [see Indications and Usage ( 1 )]. VIGAFYDE is not approved for use in adults. Clinical studies of vigabatrin did not include sufficient numbers of patients aged 65 and over to determine whether they responded differently from younger patients. Vigabatrin is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and it may be useful to monitor renal function. Oral administration of a single dose of 1.5 g of vigabatrin to elderly (≥65 years) patients with reduced creatinine clearance (<50 mL/min) was associated with moderate to severe sedation and confusion in 4 of 5 patients, lasting up to 5 days. The renal clearance of vigabatrin was 36% lower in healthy elderly subjects (≥65 years) than in young healthy males. If used in elderly patients, adjustment of dose or frequency of administration should be considered. […]

The precise mechanism of vigabatrin’s anti-seizure effect is unknown, but it is believed to be the result of its action as an irreversible inhibitor of γ-aminobutyric acid transaminase (GABA-T), the enzyme responsible for the metabolism of the inhibitory neurotransmitter GABA. This action results in increased levels of GABA in the central nervous system. No direct correlation between plasma concentration and efficacy has been established. The duration of drug effect is presumed to be dependent on the rate of enzyme re-synthesis rather than on the rate of elimination of the drug from the systemic circulation.