Felbamate (Page 5 of 8)

Effects of Felbamate on Low-Dose Combination Oral Contraceptives:

A group of 24 nonsmoking, healthy white female volunteers established on an oral contraceptive regimen containing 30 μg ethinyl estradiol and 75 μg gestodene for at least 3 months received 2,400 mg/day of felbamate from midcycle (day 15) to midcycle (day 14) of two consecutive oral contraceptive cycles. felbamate treatment resulted in a 42% decrease in the gestodene AUC 0 to 24, but no clinically relevant effect was observed on the pharmacokinetic parameters of ethinyl estradiol. No volunteer showed hormonal evidence of ovulation, but one volunteer reported intermenstrual bleeding during felbamate treatment.

Drug/Laboratory Test Interactions:

There are no known interactions of felbamate with commonly used laboratory tests.

Carcinogenesis, Mutagenesis, Impairment of Fertility:

Carcinogenicity studies were conducted in mice and rats. Mice received felbamate as a feed admixture for 92 weeks at doses of 300, 600, and 1,200 mg/kg and rats were also dosed by feed admixture for 104 weeks at doses of 30, 100, and 300 (males) or 10, 30, and 100 (females) mg/kg. The maximum doses in these studies produced steady-state plasma concentrations that were equal to or less than the steady-state plasma concentrations in epileptic patients receiving 3,600 mg/day. There was a statistically significant increase in hepatic cell adenomas in high dose male and female mice and in high-dose female rats. Hepatic hypertrophy was significantly increased in a dose-related manner in mice, primarily males, but also in females. Hepatic hypertrophy was not found in female rats. The relationship between the occurrence of benign hepatocellular adenomas and the finding of liver hypertrophy resulting from liver enzyme induction has not been examined. There was a statistically significant increase in benign interstitial cell tumors of the testes in high-dose male rats receiving felbamate. The relevance of these findings to humans is unknown.

As a result of the synthesis process, felbamate could contain small amounts of two known animal carcinogens, the genotoxic compound ethyl carbamate (urethane) and the nongenotoxic compound methyl carbamate. It is theoretically possible that a 50 kg patient receiving 3,600 mg of felbamate could be exposed to up to 0.72 micrograms of urethane and 1,800 micrograms of methyl carbamate. These daily doses are approximately 1/35,000 (urethane) and 1/5,500 (methyl carbamate) on a mg/kg basis, and 1/10,000 (urethane) and 1/1,600 (methyl carbamate) on a mg/m2 basis, of the dose levels shown to be carcinogenic in rodents. Any presence of these two compounds in felbamate used in the lifetime carcinogenicity studies was inadequate to cause tumors.

Microbial and mammalian cell assays revealed no evidence of mutagenesis in the Ames Salmonella /microsome plate test, CHO/HGPRT mammalian cell forward gene mutation assay, sister chromatid exchange assay in CHO cells, and bone marrow cytogenetics assay.

Reproduction and fertility studies in rats showed no effects on male or female fertility at oral doses of up to 13.9 times the human total daily dose of 3,600 mg on a mg/kg basis, or up to 3 times the human total daily dose on a mg/m2 basis.


Pregnancy Category C.

The incidence of malformations was not increased compared to control in offspring of rats or rabbits given doses up to 13.9 times (rat) and 4.2 times (rabbit) the human daily dose on a mg/kg basis, or 3 times (rat) and less than 2 times (rabbit) the human daily dose on a mg/m2 basis. However, in rats, there was a decrease in pup weight and an increase in pup deaths during lactation. The cause for these deaths is not known. The no effect dose for rat pup mortality was 6.9 times 549 the human dose on a mg/kg basis or 1.5 times the human dose on a mg/m2 basis.

Placental transfer of felbamate occurs in rat pups. There are, however, no studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.

To provide information regarding the effects of in utero exposure to felbamate, physicians are advised to recommend that pregnant patients taking Felbamate 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/.

Labor and Delivery:

The effect of felbamate on labor and delivery in humans is unknown.

Nursing Mothers:

Felbamate has been detected in human milk. The effect on the nursing infant is unknown (see Pregnancysection).

Pediatric Use:

The safety and effectiveness of felbamate in children other than those with Lennox-Gastaut syndrome has not been established.

Geriatric Use:

No systematic studies in geriatric patients have been conducted. Clinical studies of felbamate did not include sufficient numbers of patients aged 65 and over to determine whether they respond differently from younger patients. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dosage 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.


To report SUSPECTED ADVERSE REACTIONS, contact Viona Pharmaceuticals Inc. at 1-888-304-5011 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

The most common adverse reactions seen in association with felbamate in adults during monotherapy are anorexia, vomiting, insomnia, nausea, and headache. The most common adverse reactions seen in association with felbamate in adults during adjunctive therapy are anorexia, vomiting, insomnia, nausea, dizziness, somnolence, and headache.

The most common adverse reactions seen in association with felbamate in children during adjunctive therapy are anorexia, vomiting, insomnia, headache, and somnolence.

The dropout rate because of adverse experiences or intercurrent illnesses among adult felbamate patients was 12 percent (120/977). The dropout rate because of adverse experiences or intercurrent illnesses among pediatric felbamate patients was six percent (22/357). In adults, the body systems associated with causing these withdrawals in order of frequency were: digestive (4.3%), psychological (2.2%), whole body (1.7%), neurological (1.5%), and dermatological (1.5%). In children, the body systems associated with causing these withdrawals in order of frequency were: digestive (1.7%), neurological (1.4%), dermatological (1.4%), psychological (1.1%), and whole body (1%). In adults, specific events with an incidence of 1% or greater associated with causing these withdrawals, in order of frequency were: anorexia (1.6%), nausea (1.4%), rash (1.2%), and weight decrease (1.1%). In children, specific events with an incidence of 1% or greater associated with causing these withdrawals, in order of frequency was rash (1.1%).

Incidence in Clinical Trials:

The prescriber should be aware that the figures cited in the following table cannot be used to predict the incidence of side effects in the course of usual medical practice where patient characteristics and other factors differ from those which prevailed in the clinical trials. Similarly, the cited frequencies cannot be compared with figures obtained from other clinical investigations involving different investigators, treatments, and uses including the use of felbamate (felbamate) as adjunctive therapy where the incidence of adverse events may be higher due to drug interactions. The cited figures, however, do provide the prescribing physician with some basis for estimating the relative contribution of drug and nondrug factors to the side effect incidence rate in the population studied.


Incidence in Controlled Clinical Trials–Monotherapy Studies in Adults :

The table that follows enumerates adverse events that occurred at an incidence of 2% or more among 58 adult patients who received felbamate monotherapy at dosages of 3,600 mg/day in double-blind controlled trials. Table 3 presents reported adverse events that were classified using standard WHO-based dictionary terminology.

Table 3Adults Treatment-Emergent Adverse Event Incidence in Controlled Monotherapy Trials

*3,600 mg/day; **15 mg/kg/day

Felbamate * ( N = 58 ) Low Dose Valproate ** ( N = 50 )
Body System Event % %
Body as a Whole
Fatigue 6.9 4
Weight Decrease 3.4 0
Face Edema 3.4 0
Central Nervous System
Insomnia 8.6 4
Headache 6.9 18
Anxiety 5.2 2
Acne 3.4 0
Rash 3.4 0
Dyspepsia 8.6 2
Vomiting 8.6 2
Constipation 6.9 2
Diarrhea 5.2 0
SGPT Increased 5.2 2
Metabolic / Nutritional
Hypophosphatemia 3.4 0
Upper Respiratory Tract Infection 8.6 4
Rhinitis 6.9 0
Special Senses
Diplopia 3.4 4
Otitis Media 3.4 0
Intramenstrual Bleeding 3.4 0
Urinary Tract Infection 3.4 2

Incidence in Controlled Add-On Clinical Studies in Adults:

Table 4 enumerates adverse events that occurred at an incidence of 2% or more among 114 adult patients who received felbamate adjunctive therapy in add-on controlled trials at dosages up to 3,600 mg/day. Reported adverse events were classified using standard WHO-based dictionary terminology.

Many adverse experiences that occurred during adjunctive therapy may be a result of drug interactions. Adverse experiences during adjunctive therapy typically resolved with conversion to monotherapy, or with adjustment of the dosage of other antiepileptic drugs.

Table 4Adults Treatment-Emergent Adverse Event Incidence in Controlled Add-On Trials
Felbamate ( N = 114 ) Placebo ( N = 43 )
Body System / Event % %
Body as a Whole
Fatigue 16.8 7
Fever 2.6 4.7
Chest Pain 2.6 0
Central Nervous System
Headache 36.8 9.3
Somnolence 19.3 7
Dizziness 18.4 14
Insomnia 17.5 7
Nervousness 7 2.3
Tremor 6.1 2.3
Anxiety 5.3 4.7
Gait Abnormal 5.3 0
Depression 5.3 0
Paraesthesia 3.5 2.3
Ataxia 3.5 0
Mouth Dry 2.6 0
Stupor 2.6 0
Rash 3.5 4.7
Nausea 34.2 2.3
Anorexia 19.3 2.3
Vomiting 16.7 4.7
Dyspepsia 12.3 7
Constipation 11.4 2.3
Diarrhea 5.3 2.3
Abdominal Pain 5.3 0
SGPT Increased 3.5 0
Myalgia 2.6 0
Upper Respiratory Tract Infection 5.3 7
Sinusitis 3.5 0
Pharyngitis 2.6 0
Special Senses
Diplopia 6.1 0
Taste Perversion 6.1 0
Vision Abnormal 5.3 2.3


Incidence in a Controlled Add-On Trial in Children with Lennox-Gastaut Syndrome:

Table 5 enumerates adverse events that occurred more than once among 31 pediatric patients who received felbamate up to 45 mg/kg/day or a maximum of 3,600 mg/day. Reported adverse events were classified using standard WHO-based dictionary terminology.

Table 5Children Treatment-Emergent Adverse Event Incidence in Controlled Add-On Lennox-Gastaut Trials
Felbamate ( N = 31 ) Placebo ( N = 27 )
Body System / Event % %
Body as a Whole
Fever 22.6 11.1
Fatigue 9.7 3.7
Weight Decrease 6.5 0
Pain 6.5 0
Central Nervous System
Somnolence 48.4 11.1
Insomnia 16.1 14.8
Nervousness 16.1 18.5
Gait Abnormal 9.7 0
Headache 6.5 18.5
Thinking Abnormal 6.5 3.7
Ataxia 6.5 3.7
Urinary Incontinence 6.5 7.4
Emotional Lability 6.5 0
Miosis 6.5 0
Rash 9.7 7.4
Anorexia 54.8 14.8
Vomiting 38.7 14.8
Constipation 12.9 0
Hiccup 9.7 3.7
Nausea 6.5 0
Dyspepsia 6.5 3.7
Purpura 12.9 7.4
Leukopenia 6.5 0
Upper Respiratory Tract Infection 45.2 25.9
Pharyngitis 9.7 3.7
Coughing 6.5 0
Special Senses
Otitis Media 9.7 0

Other Events Observed in Association with the Administration of Felbamate:

In the paragraphs that follow, the adverse clinical events, other than those in the preceding tables, that occurred in a total of 977 adults and 357 children exposed to felbamate and that are reasonably associated with its use are presented. They are listed in order of decreasing frequency. Because the reports cite events observed in open-label and uncontrolled studies, the role of felbamate in their causation cannot be reliably determined.

Events are classified within body system categories and enumerated in order of decreasing frequency using the following definitions: frequent adverse events are defined as those occurring on one or more occasions in at least 1/100 patients; infrequent adverse events are those occurring in 1/100 to 1/1000 patients; and rare events are those occurring in fewer than 1/1000 patients.

Event frequencies are calculated as the number of patients reporting an event divided by the total number of patients (N=1334) exposed to felbamate.

Body as a Whole

Frequent: Weight increase, asthenia, malaise, influenza-like symptoms

Rare: anaphylactoid reaction, chest pain substernal


Frequent: Palpitation, tachycardia

Rare: supraventricular tachycardia

Central Nervous System

Frequent: Agitation, psychological disturbance, aggressive reaction

Infrequent: hallucination, euphoria, suicide attempt, migraine


Frequent: SGOT increased

Infrequent: esophagitis, appetite increased

Rare: GGT elevated


Infrequent: Lymphadenopathy, leukopenia, leukocytosis, thrombocytopenia, granulocytopenia

Rare: antinuclear factor test positive, qualitative platelet disorder, agranulocytosis


Infrequent: Hypokalemia, hyponatremia, LDH increased, alkaline phosphatase increased, hypophosphatemia

Rare: creatinine phosphokinase increased


Infrequent: Dystonia


Frequent: Pruritus

Infrequent: urticaria, bullous eruption

Rare: buccal mucous membrane swelling, Stevens-Johnson syndrome

Special Senses

Rare: Photosensitivity allergic reaction

Postmarketing Adverse Event Reports:

Voluntary reports of adverse events in patients taking felbamate (usually in conjunction with other drugs) have been received since market introduction and may have no causal relationship with the drug(s). These include the following by body system:

Body as a Whole: neoplasm, sepsis, L.E. syndrome, SIDS, sudden death, edema, hypothermia, rigors, hyperpyrexia.

Cardiovascular: atrial fibrillation, atrial arrhythmia, cardiac arrest, torsade de pointes, cardiac failure, hypotension, hypertension, flushing, thrombophlebitis, ischemic necrosis, gangrene, peripheral ischemia, bradycardia, Henoch-SchÖnlein purpura (vasculitis).

Central & Peripheral Nervous System: delusion, paralysis, mononeuritis, cerebrovascular disorder, cerebral edema, coma, manic reaction, encephalopathy, paranoid reaction, nystagmus, choreoathetosis, extrapyramidal disorder, confusion, psychosis, status epilepticus, dyskinesia, dysarthria, respiratory depression, apathy, concentration impaired.

Dermatological: abnormal body odor, sweating, lichen planus, livedo reticularis, alopecia, toxic epidermal necrolysis.

Digestive: (Refer to WARNINGS) hepatitis, hepatic failure, G.I. hemorrhage, hyperammonemia, pancreatitis, hematemesis, gastritis, rectal hemorrhage, flatulence, gingival bleeding, acquired megacolon, ileus, intestinal obstruction, enteritis, ulcerative stomatitis, glossitis, dysphagia, jaundice, gastric ulcer, gastric dilatation, gastroesophageal reflux.

Fetal Disorders: fetal death, microcephaly, genital malformation, anencephaly, encephalocele.

Hematologic: (Refer to WARNINGS) increased and decreased prothrombin time, anemia, hypochromic anemia, aplastic anemia, pancytopenia, hemolytic uremic syndrome, increased mean corpuscular volume (mcv) with and without anemia, coagulation disorder, embolism-limb, disseminated intravascular coagulation, eosinophilia, hemolytic anemia, leukemia, including myelogenous leukemia, and lymphoma, including T-cell and B-cell lymphoproliferative disorders.

Metabolic/Nutritional: hypernatremia, hypoglycemia, SIADH, hypomagnesemia, dehydration, hyperglycemia, hypocalcemia.

Musculoskeletal: arthralgia, muscle weakness, involuntary muscle contraction, rhabdomyolysis.

Respiratory: dyspnea, pneumonia, pneumonitis, hypoxia, epistaxis, pleural effusion, respiratory insufficiency, pulmonary hemorrhage, asthma.

Special Senses: hemianopsia, decreased hearing, conjunctivitis.

Urogenital: menstrual disorder, acute renal failure, hepatorenal syndrome, hematuria, urinary retention, nephrosis, vaginal hemorrhage, abnormal renal function, dysuria, placental disorder.

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