Mechanism of Action

The pharmacological activity of oxcarbazepine is primarily exerted through the 10-monohydroxy metabolite (MHD) of oxcarbazepine (see Metabolism and Excretion subsection). The precise mechanism by which oxcarbazepine and MHD exert their antiseizure effect is unknown; however, in vitro electrophysiological studies indicate that they produce blockade of voltage-sensitive sodium channels, resulting in stabilization of hyperexcited neural membranes, inhibition of repetitive neuronal firing, and diminution of propagation of synaptic impulses. These actions are thought to be important in the prevention of seizure spread in the intact brain. In addition, increased potassium conductance and modulation of high-voltage activated calcium channels may contribute to the anticonvulsant effects of the drug. No significant interactions of oxcarbazepine or MHD with brain neurotransmitter or modulator receptor sites have been demonstrated.

Pharmacodynamics

Oxcarbazepine and its active metabolite (MHD) exhibit anticonvulsant properties in animal seizure models. They protected rodents against electrically induced tonic extension seizures and, to a lesser degree, chemically induced clonic seizures, and abolished or reduced the frequency of chronically recurring focal seizures in Rhesus monkeys with aluminum implants. No development of tolerance (i.e., attenuation of anticonvulsive activity) was observed in the maximal electroshock test when mice and rats were treated daily for five days and four weeks, respectively, with oxcarbazepine or MHD.

Pharmacokinetics

Following oral administration of oxcarbazepine tablets, oxcarbazepine is completely absorbed and extensively metabolized to its pharmacologically active 10-monohydroxy metabolite (MHD). The half-life of the parent is about two hours, while the half-life of MHD is about nine hours, so that MHD is responsible for most antiepileptic activity.

Based on MHD concentrations, oxcarbazepine tablets and suspension were shown to have similar bioavailability.

After single-dose administration of oxcarbazepine tablets to healthy male volunteers under fasted conditions, the median tmax was 4.5 (range 3 to 13) hours.

In a mass balance study in people, only 2% of total radioactivity in plasma was due to unchanged oxcarbazepine, with approximately 70% present as MHD, and the remainder attributable to minor metabolites.

Effect of Food: Food has no effect on the rate and extent of absorption of oxcarbazepine from oxcarbazepine tablets. Therefore, oxcarbazepine tablets can be taken with or without food.

Steady-state plasma concentrations of MHD are reached within 2 to 3 days in patients when oxcarbazepine is given twice a day. At steady-state the pharmacokinetics of MHD are linear and show dose proportionality over the dose range of 300 to 2400 mg/day.

Distribution

The apparent volume of distribution of MHD is 49L.

Approximately 40% of MHD is bound to serum proteins, predominantly to albumin. Binding is independent of the serum concentration within the therapeutically relevant range. Oxcarbazepine and MHD do not bind to alpha-1-acid glycoprotein.

Metabolism and Excretion

Oxcarbazepine is rapidly reduced by cytosolic enzymes in the liver to its 10-monohydroxy metabolite, MHD, which is primarily responsible for the pharmacological effect of oxcarbazepine. MHD is metabolized further by conjugation with glucuronic acid. Minor amounts (4% of the dose) are oxidized to the pharmacologically inactive 10,11-dihydroxy metabolite (DHD).

Oxcarbazepine is cleared from the body mostly in the form of metabolites which are predominantly excreted by the kidneys. More than 95% of the dose appears in the urine, with less than 1% as unchanged oxcarbazepine. Fecal excretion accounts for less than 4% of the administered dose. Approximately 80% of the dose is excreted in the urine either as glucuronides of MHD (49%) or as unchanged MHD (27%); the inactive DHD accounts for approximately 3% and conjugates of MHD and oxcarbazepine account for 13% of the dose.

Special Populations

Oxcarbazepine Monotherapy Trials

Four randomized, controlled, double-blind, multicenter trials, conducted in a predominately adult population, demonstrated the efficacy of oxcarbazepine as monotherapy. Two trials compared oxcarbazepine to placebo and two trials used a randomized withdrawal design to compare a high dose (2400 mg) with a low dose (300 mg) of oxcarbazepine, after substituting oxcarbazepine 2400 mg/day for one or more antiepileptic drugs (AEDs). All doses were administered on a BID schedule. A fifth randomized, controlled, rater-blind, multicenter study, conducted in a pediatric population, failed to demonstrate a statistically significant difference between low and high dose oxcarbazepine treatment groups.

One placebo-controlled trial was conducted in 102 patients (11 to 62 years of age) with refractory partial seizures who had completed an inpatient evaluation for epilepsy surgery. Patients had been withdrawn from all AEDs and were required to have 2 to 10 partial seizures within 48 hours prior to randomization. Patients were randomized to receive either placebo or oxcarbazepine given as 1500 mg/day on Day 1 and 2400 mg/day thereafter for an additional nine days, or until one of the following three exit criteria occurred: 1) the occurrence of a fourth partial seizure, excluding Day 1, 2) two new-onset secondarily generalized seizures, where such seizures were not seen in the one-year period prior to randomization, or 3) occurrence of serial seizures or status epilepticus. The primary measure of effectiveness was a between-group comparison of the time to meet exit criteria. There was a statistically significant difference in favor of oxcarbazepine (see Figure 1), p=0.0001.

Figure 1: Kaplan-Meier Estimates of Exit Rate by Treatment Group

The second placebo-controlled trial was conducted in 67 untreated patients (8 to 69 years of age) with newly-diagnosed and recent-onset partial seizures. Patients were randomized to placebo or oxcarbazepine, initiated at 300 mg BID and titrated to 1200 mg/day (given as 600 mg BID) in six days, followed by maintenance treatment for 84 days. The primary measure of effectiveness was a between-group comparison of the time to first seizure. The difference between the two treatments was statistically significant in favor of oxcarbazepine (see Figure 2), p=0.046.

Figure 2: Kaplan-Meier Estimates of First Seizure Event Rate by Treatment Group

A third trial substituted oxcarbazepine monotherapy at 2400 mg/day for carbamazepine in 143 patients (12 to 65 years of age) whose partial seizures were inadequately controlled on carbamazepine (CBZ) monotherapy at a stable dose of 800 to 1600 mg/day, and maintained this oxcarbazepine dose for 56 days (baseline phase). Patients who were able to tolerate titration of oxcarbazepine to 2400 mg/day during simultaneous carbamazepine withdrawal were randomly assigned to either 300 mg/day of oxcarbazepine or 2400 mg/day oxcarbazepine. Patients were observed for 126 days or until one of the following four exit criteria occurred: 1) a doubling of the 28-day seizure frequency compared to baseline, 2) a two-fold increase in the highest consecutive two-day seizure frequency during baseline, 3) a single generalized seizure if none had occurred during baseline, or 4) a prolonged generalized seizure. The primary measure of effectiveness was a between-group comparison of the time to meet exit criteria. The difference between the curves was statistically significant in favor of the oxcarbazepine 2400 mg/day group (see Figure 3), p=0.0001.

Figure 3: Kaplan-Meier Estimates of Exit Rate by Treatment Group

Another monotherapy substitution trial was conducted in 87 patients (11 to 66 years of age) whose seizures were inadequately controlled on one or two AEDs. Patients were randomized to either oxcarbazepine 2400 mg/day or 300 mg/day and their standard AED regimen(s) were eliminated over the first six weeks of double-blind therapy. Double-blind treatment continued for another 84 days (total double-blind treatment of 126 days) or until one of the four exit criteria described for the previous study occurred. The primary measure of effectiveness was a between-group comparison of the percentage of patients meeting exit criteria. The results were statistically significant in favor of the oxcarbazepine 2400 mg/day group (14/34; 41.2%) compared to the oxcarbazepine 300 mg/day group (42/45; 93.3%) (p<0.0001). The time to meeting one of the exit criteria was also statistically significant in favor of the oxcarbazepine 2400 mg/day group (see Figure 4), p=0.0001.

Figure 4: Kaplan-Meier Estimates of Exit Rate by Treatment Group

A monotherapy trial was conducted in 92 pediatric patients (1 month to 16 years of age) with inadequately-controlled or new-onset partial seizures. Patients were hospitalized and randomized to either oxcarbazepine 10 mg/kg/day or were titrated up to 40 to 60 mg/kg/day within three days while withdrawing the previous AED on the second day of oxcarbazepine therapy. Seizures were recorded through continuous video-EEG monitoring from Day 3 to Day 5. Patients either completed the 5-day treatment or met one of the two exit criteria: 1) three study-specific seizures (i.e., electrographic partial seizures with a behavioral correlate), 2) a prolonged study-specific seizure. The primary measure of effectiveness was a between-group comparison of the time to meet exit criteria in which the difference between the curves was not statistically significant (p=0.904). The majority of patients from both dose groups completed the 5-day study without exiting.

Although this study failed to demonstrate an effect of oxcarbazepine as monotherapy in pediatric patients, several design elements, including the short treatment and assessment period, the absence of a true placebo, and the likely persistence of plasma levels of previously administered AEDs during the treatment period, make the results uninterpretable. For this reason, the results do not undermine the conclusion, based on pharmacokinetic/pharmacodynamic considerations, that oxcarbazepine is effective as monotherapy in pediatric patients 4 years old and older.

Oxcarbazepine Adjunctive Therapy Trials

The effectiveness of oxcarbazepine as an adjunctive therapy for partial seizures was established in two multicenter, randomized, double-blind, placebo-controlled trials, one in 692 patients (15 to 66 years of age) and one in 264 pediatric patients (3 to 17 years of age), and in one multicenter, rater-blind, randomized, age-stratified, parallel-group study comparing two doses of oxcarbazepine in 128 pediatric patients (1 month to <4 years of age).

Patients in the two placebo-controlled trials were on 1 to 3 concomitant AEDs. In both of the trials, patients were stabilized on optimum dosages of their concomitant AEDs during an 8-week baseline phase. Patients who experienced at least 8 (minimum of 1 to 4 per month) partial seizures during the baseline phase were randomly assigned to placebo or to a specific dose of oxcarbazepine in addition to their other AEDs.

In these studies, the dose was increased over a two-week period until either the assigned dose was reached, or intolerance prevented increases. Patients then entered a 14 (pediatrics) or 24-week (adults) maintenance period.

In the adult trial, patients received fixed doses of 600, 1200 or 2400 mg/day. In the pediatric trial, patients received maintenance doses in the range of 30 to 46 mg/kg/day, depending on baseline weight. The primary measure of effectiveness in both trials was a between-group comparison of the percentage change in partial seizure frequency in the double-blind treatment phase relative to baseline phase. This comparison was statistically significant in favor of oxcarbazepine at all doses tested in both trials (p=0.0001 for all doses for both trials). The number of patients randomized to each dose, the median baseline seizure rate, and the median percentage seizure rate reduction for each trial are shown in Table 1. It is important to note that in the high-dose group in the study in adults, over 65% of patients discontinued treatment because of adverse events; only 46 (27%) of the patients in this group completed the 28-week study (see ADVERSE REACTIONS section), an outcome not seen in the monotherapy studies.

1 p=0.0001; * = # per 28 days

Subset analyses of the antiepileptic efficacy of oxcarbazepine with regard to gender in these trials revealed no important differences in response between men and women. Because there were very few patients over the age of 65 in controlled trials, the effect of the drug in the elderly has not been adequately assessed.

The third adjunctive therapy trial enrolled 128 pediatric patients (1 month to <4 years of age) with inadequately-controlled partial seizures on 1 to 2 concomitant AEDs. Patients who experienced at least 2 study-specific seizures (i.e., electrographic partial seizures with a behavioral correlate) during the 72-hour baseline period were randomly assigned to either oxcarbazepine 10 mg/kg/day or were titrated up to 60 mg/kg/day within 26 days. Patients were maintained on their randomized target dose for 9 days and seizures were recorded through continuous video-EEG monitoring during the last 72 hours of the maintenance period. The primary measure of effectiveness in this trial was a between-group comparison of the change in seizure frequency per 24 hours compared to the seizure frequency at baseline. For the entire group of patients enrolled, this comparison was statistically significant in favor of oxcarbazepine 60 mg/kg/day. In this study, there was no evidence that oxcarbazepine was effective in patients below the age of 2 years (N=75).

Hyponatremia

Clinically significant hyponatremia (sodium <125 mmol/L) can develop during oxcarbazepine use. In the 14 controlled epilepsy studies 2.5% of oxcarbazepine treated patients (38/1,524) had a sodium of less than 125 mmol/L at some point during treatment, compared to no such patients assigned placebo or active control (carbamazepine and phenobarbital for adjunctive and monotherapy substitution studies, and phenytoin and valproate for the monotherapy initiation studies). Clinically significant hyponatremia generally occurred during the first three months of treatment with oxcarbazepine, although there were patients who first developed a serum sodium <125 mmol/L more than one year after initiation of therapy. Most patients who developed hyponatremia were asymptomatic but patients in the clinical trials were frequently monitored and some had their oxcarbazepine dose reduced, discontinued, or had their fluid intake restricted for hyponatremia. Whether or not these maneuvers prevented the occurrence of more severe events is unknown. Cases of symptomatic hyponatremia have been reported during post-marketing use. In clinical trials, patients whose treatment with oxcarbazepine was discontinued due to hyponatremia generally experienced normalization of serum sodium within a few days without additional treatment

Measurement of serum sodium levels should be considered for patients during maintenance treatment with oxcarbazepine, particularly if the patient is receiving other medications known to decrease serum sodium levels (for example, drugs associated with inappropriate ADH secretion) or if symptoms possibly indicating hyponatremia develop (e.g., nausea, malaise, headache, lethargy, confusion, obtundation, or increase in seizure frequency or severity).

Anaphylactic Reactions and Angioedema

Rare cases of anaphylaxis and angioedema involving the larynx, glottis, lips and eyelids have been reported in patients after taking the first or subsequent doses of oxcarbazepine. Angioedema associated with laryngeal edema can be fatal. If a patient develops any of these reactions after treatment with oxcarbazepine, the drug should be discontinued and an alternative treatment started. These patients should not be rechallenged with the drug (see WARNINGS, Patients with a Past History of Hypersensitivity Reaction to Carbamazepine subsection).

Patients with a Past History of Hypersensitivity Reaction to Carbamazepine

Patients who have had hypersensitivity reactions to carbamazepine should be informed that approximately 25% to 30% of them will experience hypersensitivity reactions with oxcarbazepine. For this reason patients should be specifically questioned about any prior experience with carbamazepine, and patients with a history of hypersensitivity reactions to carbamazepine should ordinarily be treated with oxcarbazepine only if the potential benefit justifies the potential risk. If signs or symptoms of hypersensitivity develop, oxcarbazepine should be discontinued immediately (see WARNINGS, Anaphylactic Reactions and Angioedema subsection; see PRECAUTIONS, Multi-Organ Hypersensitivity subsection).

Serious Dermatological Reactions

Serious dermatological reactions, including Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN), have been reported in both children and adults in association with oxcarbazepine use. The median time of onset for reported cases was 19 days. Such serious skin reactions may be life threatening, and some patients have required hospitalization with very rare reports of fatal outcome. Recurrence of the serious skin reactions following re-challenge with oxcarbazepine has also been reported.

The reporting rate of TEN and SJS associated with oxcarbazepine use, which is generally accepted to be an underestimate due to underreporting, exceeds the background incidence rate estimates by a factor of 3- to 10-fold. Estimates of the background incidence rate for these serious skin reactions in the general population range between 0.5 to 6 cases per million-person years. Therefore, if a patient develops a skin reaction while taking oxcarbazepine tablets, consideration should be given to discontinuing oxcarbazepine use and prescribing another antiepileptic medication.

Suicidal Behavior and Ideation

Antiepileptic drugs (AEDs), including oxcarbazepine, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.

Pooled analyses of 199 placebo-controlled clinical trials (mono- and adjunctive therapy) of 11 different AEDs showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI:1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. In these trials, which had a median treatment duration of 12 weeks, the estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in drug-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion about drug effect on suicide.

The increased risk of suicidal thoughts or behavior with AEDs was observed as early as one week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed.

The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed. The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age (5 to 100 years) in the clinical trials analyzed. Table 2 shows absolute and relative risk by indication for all evaluated AEDs.

The relative risk for suicidal thoughts or behavior was higher in clinical trials for epilepsy than in clinical trials for psychiatric or other conditions, but the absolute risk differences were similar for the epilepsy and psychiatric indications.

Anyone considering prescribing oxcarbazepine or any other AED must balance the risk of suicidal thoughts or behavior with the risk of untreated illness. Epilepsy and many other illnesses for which AEDs are prescribed are themselves associated with morbidity and mortality and an increased risk of suicidal thoughts and behavior. Should suicidal thoughts and behavior emerge during treatment, the prescriber needs to consider whether the emergence of these symptoms in any given patient may be related to the illness being treated.

Patients, their caregivers, and families should be informed that AEDs increase the risk of suicidal thoughts and behavior and should be advised of the need to be alert for the emergence or worsening of the signs and 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.

Withdrawal of AEDs

As with all antiepileptic drugs, oxcarbazepine should be withdrawn gradually to minimize the potential of increased seizure frequency.

Cognitive/Neuropsychiatric Adverse Events

Use of oxcarbazepine has been associated with central nervous system-related adverse events. The most significant of these can be classified into three general categories: 1) cognitive symptoms including psychomotor slowing, difficulty with concentration, and speech or language problems, 2) somnolence or fatigue, and 3) coordination abnormalities, including ataxia and gait disturbances.

Multi-Organ Hypersensitivity

Multi-organ hypersensitivity reactions have occurred in close temporal association (median time to detection 13 days: range 4 to 60) to the initiation of oxcarbazepine therapy in adult and pediatric patients. Although there have been a limited number of reports, many of these cases resulted in hospitalization and some were considered life threatening. Signs and symptoms of this disorder were diverse; however, patients typically, although not exclusively, presented with fever and rash associated with other organ system involvement. Other associated manifestations included lymphadenopathy, hepatitis, liver function test abnormalities, hematological abnormalities (e.g., eosinophilia, thrombocytopenia, neutropenia), pruritis, nephritis, oliguria, hepatorenal syndrome, arthralgia and asthenia. Because the disorder is variable in its expression, other organ system symptoms and signs, not noted here, may occur. If this reaction is suspected, oxcarbazepine tablets should be discontinued and an alternative treatment started. Although there are no case reports to indicate cross sensitivity with other drugs that produce this syndrome, the experience amongst drugs associated with multi-organ hypersensitivity would indicate this to be a possibility (see WARNINGS, Patients with a Past History of Hypersensitivity Reaction to Carbamazepine subsection).

Information for Patients

Anaphylactic reactions and angioedema may occur during treatment with oxcarbazepine. Patients should be advised to report immediately signs and symptoms suggesting angioedema (swelling of the face, eyes, lips, tongue or difficulty in swallowing or breathing) and to stop taking the drug until they have consulted with their physician (see WARNINGS, Anaphylactic Reactions and Angioedema subsection).

Patients who have exhibited hypersensitivity reactions to carbamazepine should be informed that approximately 25% to 30% of these patients may experience hypersensitivity reactions with oxcarbazepine. Patients should be advised that if they experience a hypersensitivity reaction while taking oxcarbazepine tablets they should consult with their physician immediately (see WARNINGS, Patients with a Past History of Hypersensitivity Reaction to Carbamazepine subsection).

Patients should be advised that serious skin reactions have been reported in association with oxcarbazepine. In the event a skin reaction should occur while taking oxcarbazepine, patients should consult with their physician immediately (see WARNINGS, Serious Dermatological Reactions subsection).

Patients should be instructed that a fever associated with other organ system involvement (rash, lymphadenopathy, etc.) may be drug related and should be reported to the physician immediately (see PRECAUTIONS, Multi-organ Hypersensitivity subsection).

Female patients of childbearing age should be warned that the concurrent use of oxcarbazepine with hormonal contraceptives may render this method of contraception less effective (see Drug Interactions subsection). Additional non-hormonal forms of contraception are recommended when using oxcarbazepine.

Patients, their caregivers, and families should be counseled that AEDs, including oxcarbazepine, may increase the risk of suicidal thoughts and behavior and should be advised 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.

Caution should be exercised if alcohol is taken in combination with oxcarbazepine therapy, due to a possible additive sedative effect.

Patients should be advised that oxcarbazepine may cause dizziness and somnolence. Accordingly, patients should be advised not to drive or operate machinery until they have gained sufficient experience on oxcarbazepine to gauge whether it adversely affects their ability to drive or operate machinery.

Patients should be encouraged to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry if they become pregnant. This registry is collecting information about the safety of antiepileptic drugs during pregnancy. To enroll, patients can call the toll free number 1-888-233-2334 (see PRECAUTIONS, Pregnancy Category C subsection).

Laboratory Tests

Serum sodium levels below 125 mmol/L have been observed in patients treated with oxcarbazepine (see WARNINGS section). Experience from clinical trials indicates that serum sodium levels return toward normal when the oxcarbazepine dosage is reduced or discontinued, or when the patient was treated conservatively (e.g., fluid restriction).

Laboratory data from clinical trials suggest that oxcarbazepine use was associated with decreases in T4, without changes in T3 or TSH.

Drug Interactions

Oxcarbazepine can inhibit CYP2C19 and induce CYP3A4/5 with potentially important effects on plasma concentrations of other drugs. In addition, several AEDs that are cytochrome P450 inducers can decrease plasma concentrations of oxcarbazepine and MHD.

Oxcarbazepine was evaluated in human liver microsomes to determine its capacity to inhibit the major cytochrome P450 enzymes responsible for the metabolism of other drugs. Results demonstrate that oxcarbazepine and its pharmacologically active 10-monohydroxy metabolite (MHD) have little or no capacity to function as inhibitors for most of the human cytochrome P450 enzymes evaluated (CYP1A2, CYP2A6, CYP2C9, CYP2D6, CYP2E1, CYP4A9 and CYP4A11) with the exception of CYP2C19 and CYP3A4/5. Although inhibition of CYP3A4/5 by oxcarbazepine and MHD did occur at high concentrations, it is not likely to be of clinical significance. The inhibition of CYP2C19 by oxcarbazepine and MHD, however, is clinically relevant (see below).

In vitro, the UDP-glucuronyl transferase level was increased, indicating induction of this enzyme. Increases of 22% with MHD and 47% with oxcarbazepine were observed. As MHD, the predominant plasma substrate, is only a weak inducer of UDP-glucuronyl transferase, it is unlikely to have an effect on drugs that are mainly eliminated by conjugation through UDP-glucuronyl transferase (e.g., valproic acid, lamotrigine).

In addition, oxcarbazepine and MHD induce a subgroup of the cytochrome P450 3A family (CYP3A4 and CYP3A5) responsible for the metabolism of dihydropyridine calcium antagonists, oral contraceptives, resulting in a lower plasma concentration of these drugs.

As binding of MHD to plasma proteins is low (40%), clinically significant interactions with other drugs through competition for protein binding sites are unlikely.

Carcinogenesis/Mutagenesis/Impairment of Fertility

In two-year carcinogenicity studies, oxcarbazepine was administered in the diet at doses of up to 100 mg/kg/day to mice and by gavage at doses of up to 250 mg/kg to rats, and the pharmacologically active 10-hydroxy metabolite (MHD) was administered orally at doses of up to 600 mg/kg/day to rats. In mice, a dose-related increase in the incidence of hepatocellular adenomas was observed at oxcarbazepine doses ≥70 mg/kg/day or approximately 0.1 times the maximum recommended human dose (MRHD) on a mg/m2 basis. In rats, the incidence of hepatocellular carcinomas was increased in females treated with oxcarbazepine at doses ≥25 mg/kg/day (0.1 times the MRHD on a mg/m2 basis), and incidences of hepatocellular adenomas and/or carcinomas were increased in males and females treated with MHD at doses of 600 mg/kg/day (2.4 times the MRHD on a mg/m2 basis) and ≥250 mg/kg/day (equivalent to the MRHD on a mg/m2 basis), respectively. There was an increase in the incidence of benign testicular interstitial cell tumors in rats at 250 mg oxcarbazepine/kg/day and at ≥250 mg MHD/kg/day, and an increase in the incidence of granular cell tumors in the cervix and vagina in rats at 600 mg MHD/kg/day.

      Oxcarbazepine increased mutation frequencies in the Ames test in vitro in the absence of metabolic activation in one of five bacterial strains. Both oxcarbazepine and MHD produced increases in chromosomal aberrations and polyploidy in the Chinese hamster ovary assay in vitro in the absence of metabolic activation. MHD was negative in the Ames test, and no mutagenic or clastogenic activity was found with either oxcarbazepine or MHD in V79 Chinese hamster cells in vitro. Oxcarbazepine and MHD were both negative for clastogenic or aneugenic effects (micronucleus formation) in an in vivo rat bone marrow assay.

In a fertility study in which rats were administered MHD (50, 150, or 450 mg/kg) orally prior to and during mating and early gestation, estrous cyclicity was disrupted and numbers of corpora lutea, implantations, and live embryos were reduced in females receiving the highest dose (approximately two times the MRHD on a mg/m2 basis).

Pregnancy Category C

Increased incidences of fetal structural abnormalities and other manifestations of developmental toxicity (embryolethality, growth retardation) were observed in the offspring of animals treated with either oxcarbazepine or its active 10-hydroxy metabolite (MHD) during pregnancy at doses similar to the maximum recommended human dose.

When pregnant rats were given oxcarbazepine (30, 300, or 1000 mg/kg) orally throughout the period of organogenesis, increased incidences of fetal malformations (craniofacial, cardiovascular, and skeletal) and variations were observed at the intermediate and high doses (approximately 1.2 and 4 times, respectively, the maximum recommended human dose [MRHD] on a mg/m2 basis). Increased embryofetal death and decreased fetal body weights were seen at the high dose. Doses ≥300 mg/kg were also maternally toxic (decreased body weight gain, clinical signs), but there is no evidence to suggest that teratogenicity was secondary to the maternal effects.

In a study in which pregnant rabbits were orally administered MHD (20, 100, or 200 mg/kg) during organogenesis, embryofetal mortality was increased at the highest dose (1.5 times the MRHD on a mg/m2 basis). This dose produced only minimal maternal toxicity.

In a study in which female rats were dosed orally with oxcarbazepine (25, 50, or 150 mg/kg) during the latter part of gestation and throughout the lactation period, a persistent reduction in body weights and altered behavior (decreased activity) were observed in offspring exposed to the highest dose (0.6 times the MRHD on a mg/m2 basis). Oral administration of MHD (25, 75, or 250 mg/kg) to rats during gestation and lactation resulted in a persistent reduction in offspring weights at the highest dose (equivalent to the MRHD on a mg/m2 basis).

There are no adequate and well-controlled clinical studies of oxcarbazepine in pregnant women; however, oxcarbazepine is closely related structurally to carbamazepine, which is considered to be teratogenic in humans. Given this fact, and the results of the animal studies described, it is likely that oxcarbazepine is a human teratogen. Oxcarbazepine 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 oxcarbazepine tablets, physicians are advised to recommend that pregnant patients taking oxcarbazepine tablets 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 oxcarbazepine on labor and delivery in humans has not been evaluated.

Nursing Mothers

Oxcarbazepine and its active metabolite (MHD) are excreted in human breast milk. A milk-to-plasma concentration ratio of 0.5 was found for both. Because of the potential for serious adverse reactions to oxcarbazepine in nursing infants, a decision should be made about whether to discontinue nursing or to discontinue the drug in nursing women, taking into account the importance of the drug to the mother.

Patients with Renal Impairment

In renally-impaired patients (creatinine clearance <30 mL/min), the elimination half-life of MHD is prolonged with a corresponding two-fold increase in AUC (see CLINICAL PHARMACOLOGY, Pharmacokinetics subsection). Oxcarbazepine therapy should be initiated at one-half the usual starting dose and increased, if necessary, at a slower than usual rate until the desired clinical response is achieved.

Pediatric Use

Oxcarbazepine is indicated for use as adjunctive therapy for partial seizures in patients aged 2 to 16 years. Oxcarbazepine is also indicated as monotherapy for partial seizures in patients aged 4 to 16 years. Oxcarbazepine has been given to 898 patients between the ages of 1 month to 17 years in controlled clinical trials (332 treated as monotherapy) and about 677 patients between the ages of 1 month to 17 years in other trials. (See ADVERSE REACTIONS section for a description of the adverse events associated with oxcarbazepine use in this population.)

Geriatric Use

There were 52 patients over age 65 in controlled clinical trials and 565 patients over the age of 65 in other trials. Following administration of single (300 mg) and multiple (600 mg/day) doses of oxcarbazepine in elderly volunteers (60 to 82 years of age), the maximum plasma concentrations and AUC values of MHD were 30% to 60% higher than in younger volunteers (18 to 32 years of age). Comparisons of creatinine clearance in young and elderly volunteers indicate that the difference was due to age-related reductions in creatinine clearance.

Most Common Adverse Events in All Clinical Studies

Adjunctive Therapy/Monotherapy in Adults Previously Treated with other AEDs: The most commonly observed (≥5%) adverse experiences seen in association with oxcarbazepine and substantially more frequent than in placebo-treated patients were: Dizziness, somnolence, diplopia, fatigue, nausea, vomiting, ataxia, abnormal vision, abdominal pain, tremor, dyspepsia, abnormal gait.

Approximately 23% of these 1,537 adult patients discontinued treatment because of an adverse experience. The adverse experiences most commonly associated with discontinuation were: Dizziness (6.4%), diplopia (5.9%), ataxia (5.2%), vomiting (5.1%), nausea (4.9%), somnolence (3.8%), headache (2.9%), fatigue (2.1%), abnormal vision (2.1%), tremor (1.8%), abnormal gait (1.7%), rash (1.4%), hyponatremia (1%).

Monotherapy in Adults Not Previously Treated with other AEDs: The most commonly observed (≥5%) adverse experiences seen in association with oxcarbazepine in these patients were similar to those in previously treated patients.

Approximately 9% of these 295 adult patients discontinued treatment because of an adverse experience. The adverse experiences most commonly associated with discontinuation were: Dizziness (1.7%), nausea (1.7%), rash (1.7%), headache (1.4%).

Adjunctive Therapy/Monotherapy in Pediatric Patients 4 Years Old and Above Previously Treated with other AEDs: The most commonly observed (≥5%) adverse experiences seen in association with oxcarbazepine in these patients were similar to those seen in adults.

Approximately 11% of these 456 pediatric patients discontinued treatment because of an adverse experience. The adverse experiences most commonly associated with discontinuation were: Somnolence (2.4%), vomiting (2%), ataxia (1.8%), diplopia (1.3%), dizziness (1.3%), fatigue (1.1%), nystagmus (1.1%).

Monotherapy in Pediatric Patients 4 Years Old and Above Not Previously Treated with other AEDs: The most commonly observed (≥5%) adverse experiences seen in association with oxcarbazepine in these patients were similar to those in adults.

Approximately 9.2% of 152 pediatric patients discontinued treatment because of an adverse experience. The adverse experiences most commonly associated (≥1%) with discontinuation were rash (5.3%) and maculopapular rash (1.3%).

Adjunctive Therapy/Monotherapy in Pediatric Patients 1 Month to <4 Years Old Previously Treated or Not Previously Treated with other AEDs: The most commonly observed (≥5%) adverse experiences seen in association with oxcarbazepine in these patients were similar to those seen in older children and adults except for infections and infestations which were more frequently seen in these younger children.

Approximately 11% of these 241 pediatric patients discontinued treatment because of an adverse experience. The adverse experiences most commonly associated with discontinuation were: Convulsions (3.7%), status epilepticus (1.2%), and ataxia (1.2%).

Incidence in Controlled Clinical Studies: The prescriber should be aware that the figures in Tables 4, 5, 6 and 7 cannot be used to predict the frequency of adverse experiences in the course of usual medical practice where patient characteristics and other factors may differ from those prevailing during clinical studies. Similarly, the cited frequencies cannot be directly compared with figures obtained from other clinical investigations involving different treatments, uses, or investigators. An inspection of these frequencies, however, does provide the prescriber with one basis to estimate the relative contribution of drug and nondrug factors to the adverse event incidences in the population studied.

Controlled Clinical Studies of Adjunctive Therapy/Monotherapy in Adults Previously Treated with other AEDs:Table 4 lists treatment-emergent signs and symptoms that occurred in at least 2% of adult patients with epilepsy treated with oxcarbazepine or placebo as adjunctive treatment and were numerically more common in the patients treated with any dose of oxcarbazepine. Table 5 lists treatment-emergent signs and symptoms in patients converted from other AEDs to either high dose oxcarbazepine or low dose (300 mg) oxcarbazepine. Note that in some of these monotherapy studies patients who dropped out during a preliminary tolerability phase are not included in the tables.

Controlled Clinical Study of Monotherapy in Adults Not Previously Treated with other AEDs:Table 6 lists treatment-emergent signs and symptoms in a controlled clinical study of monotherapy in adults not previously treated with other AEDs that occurred in at least 2% of adult patients with epilepsy treated with oxcarbazepine or placebo and were numerically more common in the patients treated with oxcarbazepine.

Controlled Clinical Studies of Adjunctive Therapy/Monotherapy in Pediatric Patients Previously Treated with other AEDs:  Table 7 lists treatment-emergent signs and symptoms that occurred in at least 2% of pediatric patients with epilepsy treated with oxcarbazepine or placebo as adjunctive treatment and were numerically more common in the patients treated with oxcarbazepine.

Other Events Observed in Association with the Administration of Oxcarbazepine

In the paragraphs that follow, the adverse events, other than those in the preceding tables or text, that occurred in a total of 565 children and 1,574 adults exposed to oxcarbazepine and that are reasonably likely to be related to drug use are presented. Events common in the population, events reflecting chronic illness and events likely to reflect concomitant illness are omitted particularly if minor. They are listed in order of decreasing frequency. Because the reports cite events observed in open label and uncontrolled trials, the role of oxcarbazepine in their causation cannot be reliably determined.

Body as a Whole:  Fever, malaise, pain chest precordial, rigors, weight decrease.

Cardiovascular System:  Bradycardia, cardiac failure, cerebral hemorrhage, hypertension, hypotension postural, palpitation, syncope, tachycardia.

Digestive System:  Appetite increased, blood in stool, cholelithiasis, colitis, duodenal ulcer, dysphagia, enteritis, eructation, esophagitis, flatulence, gastric ulcer, gingival bleeding, gum hyperplasia, hematemesis, hemorrhage rectum, hemorrhoids, hiccup, mouth dry, pain biliary, pain right hypochondrium, retching, sialoadenitis, stomatitis, stomatitis ulcerative.

Hemic and Lymphatic System:  Leukopenia, thrombocytopenia.

Laboratory Abnormality:  Gamma-GT increased, hyperglycemia, hypocalcemia, hypoglycemia, hypokalemia, liver enzymes elevated, serum transaminase increased.

Musculoskeletal System:  Hypertonia muscle.

Nervous System:  Aggressive reaction, amnesia, anguish, anxiety, apathy, aphasia, aura, convulsions aggravated, delirium, delusion, depressed level of consciousness, dysphonia, dystonia, emotional lability, euphoria, extrapyramidal disorder, feeling drunk, hemiplegia, hyperkinesia, hyperreflexia, hypoesthesia, hypokinesia, hyporeflexia, hypotonia, hysteria, libido decreased, libido increased, manic reaction, migraine, muscle contractions involuntary, nervousness, neuralgia, oculogyric crisis, panic disorder, paralysis, paroniria, personality disorder, psychosis, ptosis, stupor, tetany.

Respiratory System:  Asthma, dyspnea, epistaxis, laryngismus, pleurisy.

Skin and Appendages:  Acne, alopecia, angioedema, bruising, dermatitis contact, eczema, facial rash, flushing, folliculitis, heat rash, hot flushes, photosensitivity reaction, pruritus genital, psoriasis, purpura, rash erythematous, rash maculopapular, vitiligo, urticaria.

Special Senses:  Accommodation abnormal, cataract, conjunctival hemorrhage, edema eye, hemianopia, mydriasis, otitis externa, photophobia, scotoma, taste perversion, tinnitus, xerophthalmia.

Surgical and Medical Procedures:  Procedure dental oral, procedure female reproductive, procedure musculoskeletal, procedure skin.

Urogenital and Reproductive System:  Dysuria, hematuria, intermenstrual bleeding, leukorrhea, menorrhagia, micturition frequency, pain renal, pain urinary tract, polyuria, priapism, renal calculus.

Other:  Systemic lupus erythematosus.

Post-Marketing and Other Experience

The following adverse events not seen in controlled clinical trials have been observed in named patient programs or post-marketing experience:

Body as a Whole: Multi-organ hypersensitivity disorders characterized by features such as rash, fever, lymphadenopathy, abnormal liver function tests, eosinophilia and arthralgia (see PRECAUTIONS, Multi-Organ Hypersensitivity subsection).

Anaphylaxis (see WARNINGS, Anaphylactic Reactions and Angioedema subsection).

Skin and Appendages: Erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis (see WARNINGS, Serious Dermatological Reactions subsection).

Abuse

The abuse potential of oxcarbazepine has not been evaluated in human studies.

Dependence

Intragastric injections of oxcarbazepine to four cynomolgus monkeys demonstrated no signs of physical dependence as measured by the desire to self-administer oxcarbazepine by lever pressing activity.

Human Overdose Experience

Isolated cases of overdose with oxcarbazepine have been reported. The maximum dose taken was approximately 24,000 mg. All patients recovered with symptomatic treatment.

Treatment and Management

There is no specific antidote. Symptomatic and supportive treatment should be administered as appropriate. Removal of the drug by gastric lavage and/or inactivation by administering activated charcoal should be considered.

Adults

Pediatric Patients

Patients with Hepatic Impairment

In general, dose adjustments are not required in patients with mild-to-moderate hepatic impairment (see CLINICAL PHARMACOLOGY, Pharmacokinetics, Special Populations subsection).

Patients with Renal Impairment

In patients with impaired renal function (creatinine clearance < 30 mL/min) oxcarbazepine therapy should be initiated at one-half the usual starting dose (300 mg/day) and increased slowly to achieve the desired clinical response (see CLINICAL PHARMACOLOGY, Pharmacokinetics, Special Populations subsection).

150 mg Film-Coated Tablets:  yellow colour, capsule shaped, biconvex, coated tablets scored and debossed with '183' on one side and scored on other side.

Bottle of 90:                                  NDC 33261-0684-90

300 mg Film-Coated Tablets:  yellow colour, capsule shaped, biconvex, coated tablets scored and debossed with '184' on one side and scored on other side.

Bottle of 60:                                 NDC 33261-0841-60

Bottle of 90:                                 NDC 33261-0841-90

600 mg Film-Coated Tablets:  yellow colour, capsule shaped, biconvex, coated tablets scored and debossed with '185' on one side and scored on other side.

Bottle of 60:                                 NDC 33261-0842-60

Store at 25°C (77°F); excursions permitted to 15°C-30°C (59°F-86°F) [see USP Controlled Room Temperature]. Dispense in tight container (USP).