Sabril Drug Information

Refractory Complex Partial Seizures (CPS) SABRIL is indicated as adjunctive therapy for adults and pediatric patients 2 years of age and older with refractory complex partial seizures who have inadequately responded to several alternative treatments and for whom the potential benefits outweigh the risk of vision loss. SABRIL is not indicated as a first line agent for complex partial seizures.

Infantile Spasms (IS) SABRIL is indicated as monotherapy for pediatric patients with infantile spasms 1 month to 2 years of age for whom the potential benefits outweigh the potential risk of vision loss.

Important Dosing and Administration Instructions Dosing Use the lowest dosage and shortest exposure to SABRIL consistent with clinical objectives. The SABRIL dosing regimen depends on the indication, age group, weight, and dosage form (tablets or for oral solution). Patients with impaired renal function require dose adjustment.

Monitoring of SABRIL plasma concentrations to optimize therapy is not helpful. Administration SABRIL is given orally with or without food. SABRIL for oral solution should be mixed with water prior to administration.

A calibrated measuring device is recommended to measure and deliver the prescribed dose accurately. A household teaspoon or tablespoon is not an adequate measuring device. If a decision is made to discontinue SABRIL, the dose should be gradually reduced.

Refractory Complex Partial Seizures Adults (Patients 17 Years of Age and Older) Treatment should be initiated at 1000 mg/day (500 mg twice daily). Total daily dose may be increased in 500 mg increments at weekly intervals depending on response. The recommended dose of SABRIL in adults is 3000 mg/day (1500 mg twice daily).

A 6000 mg/day dose has not been shown to confer additional benefit compared to the 3000 mg/day dose and is associated with an increased incidence of adverse events. In controlled clinical studies in adults with complex partial seizures, SABRIL was tapered by decreasing the daily dose 1000 mg/day on a weekly basis until discontinued. Pediatric (Patients 2 to 16 Years of Age) The recommended dosage is based on body weight and administered as two divided doses, as shown in Table 1.

The dosage may be increased in weekly intervals to the total daily maintenance dosage, depending on response. Pediatric patients weighing more than 60 kg should be dosed according to adult recommendations. Table 1.

CPS Dosing Recommendations for Pediatric Patients Weighing 10 kg up to 60 kg Body Weight Total Daily* Starting Dose Total Daily* Maintenance Dose In patients with refractory complex partial seizures, SABRIL should be withdrawn if a substantial clinical benefit is not observed within 3 months of initiating treatment. If, in the clinical judgment of the prescriber, evidence of treatment failure becomes obvious earlier than 3 months, treatment should be discontinued at that time. In a controlled study in pediatric patients with complex partial seizures, SABRIL was tapered by decreasing the daily dose by one third every week for three weeks.

Infantile Spasms

The initial daily dosing is 50 mg/kg/day given in two divided doses (25 mg/kg twice daily); subsequent dosing can be titrated by 25 mg/kg/day to 50 mg/kg/day increments every 3 days, up to a maximum of 150 mg/kg/day given in 2 divided doses (75 mg/kg twice daily). Table 2 provides the volume of the 50 mg/mL dosing solution that should be administered as individual doses in infants of various weights. In patients with infantile spasms, SABRIL should be withdrawn if a substantial clinical benefit is not observed within 2 to 4 weeks.

In a controlled clinical study in patients with infantile spasms, SABRIL was tapered by decreasing the daily dose at a rate of 25 mg/kg to 50 mg/kg every 3 to 4 days.

Patients with Renal Impairment SABRIL is primarily eliminated through the kidney. Infants Information about how to adjust the dose in infants with renal impairment is unavailable. Adult and pediatric patients 2 years and older Mild renal impairment (CLcr >50 to 80 mL/min): dose should be decreased by 25% Moderate renal impairment (CLcr >30 to 50 mL/min): dose should be decreased by 50% Severe renal impairment (CLcr >10 to 30 mL/min): dose should be decreased by 75% CLcr in mL/min may be estimated from serum creatinine (mg/dL) using the following formulas: Patients 2 to <12 years old: CLcr (mL/min/1.73 m 2 ) = (K × Ht) / Scr height (Ht) in cm; serum creatinine (Scr) in mg/dL K (proportionality constant): Female Child (<12 years): K=0.55; Male Child (<12 years): K=0.70 Adult and pediatric patients 12 years or older: CLcr (mL/min) = × weight ( kg ) / (× 0.85 for female patients ) The effect of dialysis on SABRIL clearance has not been adequately studied.

Preparation and Administration Instructions for SABRIL for oral solution If using SABRIL for oral solution, physicians should review and discuss the Medication Guide and instructions for mixing and giving SABRIL with the patient or caregiver(s). Physicians should confirm that patients or caregiver(s) understand how to mix SABRIL powder with water and administer the correct daily dose. Empty the entire contents of each 500 mg packet into a clean cup, and dissolve in 10 mL of cold or room temperature water per packet.

Administer the resulting solution using the 3 mL or 10 mL oral syringe provided by the pharmacy. The concentration of the final solution is 50 mg/mL. Table 3 below describes how many packets and how many milliliters (mL) of water will be needed to prepare each individual dose.

The concentration after reconstitution is 50 mg/mL. Discard the resulting solution if it is not clear (or free of particles) and colorless. Each individual dose should be prepared and used immediately.

Discard any unused portion of the solution after administering the correct dose.

Clinical Trial 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. In U.S. and primary non-U.S. clinical studies of 4,079 SABRIL-treated patients, the most common (≥5%) adverse reactions associated with the use of SABRIL in combination with other AEDs were headache, somnolence, fatigue, dizziness, convulsion, nasopharyngitis, weight gain, upper respiratory tract infection, visual field defect, depression, tremor, nystagmus, nausea, diarrhea, memory impairment, insomnia, irritability, abnormal coordination, blurred vision, diplopia, vomiting, influenza, pyrexia, and rash. The adverse reactions most commonly associated with SABRIL treatment discontinuation in ≥1% of patients were convulsion and depression.

In patients with infantile spasms, the adverse reactions most commonly associated with SABRIL treatment discontinuation in ≥1% of patients were infections, status epilepticus, developmental coordination disorder, dystonia, hypotonia, hypertonia, weight gain, and insomnia. Refractory C omplex Partial Seizures Adults Table 5 lists the adverse reactions that occurred in ≥2% and more than one patient per SABRIL-treated group and that occurred more frequently than in placebo patients from 2 U.S. adjunctive clinical studies of refractory CPS in adults. years of age Table 6 lists adverse reactions from controlled clinical studies of pediatric patients receiving SABRIL or placebo as adjunctive therapy for refractory complex partial seizures. Adverse reactions that are listed occurred in at least 2% of SABRIL-treated patients and more frequently than placebo.

In a dose response study of low-dose (18-36 mg/kg/day) versus high-dose (100-148 mg/kg/day) SABRIL, no clear correlation between dose and incidence of adverse reactions was observed. The adverse reactions (≥5% in either dose group) are summarized in Table 7.

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of SABRIL. 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. Adverse reactions are categorized by system organ class.

Birth Defects: Congenital cardiac defects, congenital external ear anomaly, congenital hemangioma, congenital hydronephrosis, congenital male genital malformation, congenital oral malformation, congenital vesicoureteric reflux, dentofacial anomaly, dysmorphism, fetal anticonvulsant syndrome, hamartomas, hip dysplasia, limb malformation, limb reduction defect, low set ears, renal aplasia, retinitis pigmentosa, supernumerary nipple, talipes 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

Antiepileptic Drugs Phenytoin

Although phenytoin dose adjustments are not routinely required, dose adjustment of phenytoin should be considered if clinically indicated, since SABRIL may cause a moderate reduction in total phenytoin plasma levels. Clonazepam SABRIL may moderately increase the C max of clonazepam resulting in an increase of clonazepam-associated adverse reactions. Other AEDs There are no clinically significant pharmacokinetic interactions between SABRIL and either phenobarbital or sodium valproate.

Based on population pharmacokinetics, carbamazepine, clorazepate, primidone, and sodium valproate appear to have no effect on plasma concentrations of vigabatrin.

Oral Contraceptives SABRIL is unlikely to affect the efficacy of steroid oral contraceptives.

Drug-Laboratory Test Interactions

SABRIL 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 SABRIL may preclude the use of these markers, especially ALT, to detect early hepatic injury.

SABRIL 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).

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AEDs, including SABRIL, during pregnancy. Encourage women who are taking SABRIL 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 SABRIL in pregnant women. Limited available data from case reports and cohort studies pertaining to SABRIL 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, SABRIL 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 2-4% and 15-20%, 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 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 4-65) 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.

Pediatric Use The safety and effectiveness of SABRIL as adjunctive treatment of refractory complex partial seizures in pediatric patients 2 to 16 years of age have been established and is supported by three double-blind, placebo-controlled studies in patients 3 to 16 years of age, adequate and well-controlled studies in adult patients, pharmacokinetic data from patients 2 years of age and older, and additional safety information in patients 2 years of age. The dosing recommendation in this population varies according to age group and is weight-based. Adverse reactions in this pediatric population are similar to those observed in the adult population.

The safety and effectiveness of SABRIL as monotherapy for pediatric patients with infantile spasms (1 month to 2 years of age) have been established. Safety and effectiveness as adjunctive treatment of refractory complex partial seizures in pediatric patients below the age of 2 and as 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. Abnormal MRI signal changes and Intramyelinic Edema (IME) in infants and young children being treated with SABRIL have been observed.

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 4-65) 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 22-112) 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.

Signs, Symptoms, and Laboratory Findings of Overdosage

Confirmed and/or suspected vigabatrin overdoses have been reported during clinical trials and in post marketing surveillance. No vigabatrin overdoses resulted in death. Nearly half the cases involved multiple drug ingestions including carbamazepine, barbiturates, benzodiazepines, lamotrigine, valproic acid, acetaminophen, and/or chlorpheniramine.

Coma, unconsciousness, and/or drowsiness were described in the majority of cases of vigabatrin overdose. Other less commonly reported symptoms included vertigo, psychosis, apnea or respiratory depression, bradycardia, agitation, irritability, confusion, headache, hypotension, abnormal behavior, increased seizure activity, status epilepticus, and speech disorder. These symptoms resolved with supportive care.

Management of Overdosage There is no specific antidote for SABRIL overdose. Standard measures to remove unabsorbed drug should be used, including elimination by emesis or gastric lavage. Supportive measures should be employed, including monitoring of vital signs and observation of the clinical status of the patient.

In an in vitro study, activated charcoal did not significantly adsorb vigabatrin. The effectiveness of hemodialysis in the treatment of SABRIL overdose is unknown. In isolated case reports in renal failure patients receiving therapeutic doses of vigabatrin, hemodialysis reduced vigabatrin plasma concentrations by 40% to 60%.