Lamotrix

Lamotrix

lamotrigine

Manufacturer:

Medochemie

Distributor:

Medochemie
Full Prescribing Info
Contents
Lamotrigine.
Description
"Lamotrix" tablets: each tablet contains 50 mg or 100mg of lamotrigine.
Excipients/Inactive ingredients: All the strengths of lamotrigine tablets contain lactose monohydrate, cellulose microcrystalline, sodium starch glycolate, povidone, magnesium stearate and iron oxide yellow (E172) as the inactive ingredients.
Action
ATC Code: N03AX09.
Pharmacology: Pharmacodynamics: Mechanism of action: The results of pharmacological studies suggest that lamotrigine is a use-dependent blocker of voltage gated sodium channels. It produces a use-and voltage-dependent block of sustained repetitive firing in cultured neurons and inhibits pathological release of glutamate, the amino acid which plays a key role in the generation of epileptic seizures as well as inhibiting glutamate evoke bursts of action potentials.
Pharmacodynamic effects: In tests designed to evaluate the central nervous system effects of drug, the results obtained using doses of 240 mg lamotrigine administered to healthy volunteers did not differ from placebo, whereas both 1000 mg phenytoin and 10mg diazepam each significantly impaired fine visual motor co-ordination and eye movements, increased body sway and produced subjective sedative effects.
In another study, single oral doses of 600 mg carbamazepine significantly impaired fine visual motor co-ordination and eye movements, while increasing both body sway and heart rate, whereas results with lamotrigine at doses of 150 mg and 300 mg did not differ from placebo.
Melanin binding: Lamotrigine binds to melanin-containing tissues, e.g., in the eye and pigmented skin. It has been found in the uveal tract up to 52 weeks after a single dose in rodents.
Clinical Studies: Clinical efficacy and safety of adjunctive therapy in patients aged 1 to 24 months with partial seizures: The effectiveness of lamotrigine as adjunctive therapy in patients aged 1 to 24 months with partial seizures wasevaluated in a multi-centre, double-blind, placebo controlled add-on trial (Study LAM20006). Lamotrigine was added to 1 or 2 AEDs during an open-label phase (n=177).
Lamotrigine was given on alternate days or once daily if an initial total dose or dose titration step of less than 2 mg was required. Serum levels were measured at the end of week 2 of titration and the subsequent dose either reduced or not increased if the concentration exceeded 0.41 μg/mL, the expected concentration in adults at this time point. Dose reductions of up to 90% were required in some patients at the end of week 2. If valproate was used as an AED, lamotrigine was added only after an infant had been on valproate for 6 months without liver function test abnormalities.
The safety and efficacy of lamotrigine in patients weighing less than 6.7 kg, and taking valproate or AEDs other than carbamazepine, phenytoin, phenobarbital or primidone has not been evaluated. Patients achieving a 40% or greater reduction in partial seizure frequency (n=38) were randomised to either gradual withdrawal to placebo (n=19) or continued lamotrigine (n=19) for up to 8 weeks. The primary efficacy endpoint was based on the difference in the proportion of subjects receiving lamotrigine or placebo who met defined escape criteria. The escape criteria allowed the withdrawal of subjects from the study if their epilepsy conditions showed any signs of clinical deterioration. Statistical significance on the primary endpoint was not achieved; however, fewer patients met escape criteria on lamotrigine (58%) compared with placebo (84%) and took a longer time to meet escape criteria (42 versus 22 days).
A total of 256 subjects between 1 to 24 months of age have been exposed to lamotrigine in the dose range 1 to 15 mg/kg/day for up to 72 weeks. The safety profile of lamotrigine in children aged 1 month to 2 years was similar to that in older children except that clinically significant worsening of seizures (>=50%) was reported more often in children under 2 years of age (26%) as compared to older children (14%).
Clinical efficacy in the prevention of depressive episodes in patients with bipolar disorder: Adults (18 years of age and over): Two pivotal studies have demonstrated efficacy in the prevention of depressive episodes in patients with bipolar disorder.
Clinical study SCAB20003 was a multicenter, double-blind, double-dummy, placebo and lithium-controlled, randomized fixed dose evaluation of the long-term prevention of relapse and recurrence of depression and/or mania in patients with bipolar I disorder who had recently or were currently experiencing a major depressive episode. Once stabilized using lamotrigine monotherapy or lamotrigine plus psychotropic medication, patients were randomly assigned into one of five treatment groups: lamotrigine (50, 200, 400 mg/day), lithium (serum levels of 0.8 to 1.1 mMOL/L) or placebo for a maximum of 76 weeks (18 months). Treatment regimens were maintained until an emerging mood episode (depressive or manic) deemed it necessary to intervene with additional pharmacotherapy or electroconvulsive therapy (ECT).
The primary endpoint was "Time to Intervention for a Mood Episode (TIME)", where the interventions were either additional pharmacotherapy or ECT. This endpoint was analyzed using three methods of handling data from patients who were withdrawn prior to having an intervention. The p-values for these analyses ranged from 0.003 to 0.029. In supportive analyses of time to first depressive episode and time to first manic/hypomanic or mixed episode, the lamotrigine patients had longer times to first depressive episode than placebo patients (p=0.047), and the treatment difference with respect to time to manic/hypomanic or mixed episodes was not statistically significant. Clinical study SCAB2006 was a multicenter, double-blind, double-dummy, placebo and lithium-controlled, randomized, flexible dose evaluation of lamotrigine in the long-term prevention of relapse and recurrence of mania and/or depression in patients with bipolar I disorder who had recently or were currently experiencing a manic or hypomanic episode. Once stabilized using lamotrigine monotherapy or lamotrigine plus psychotropic medication, patients were randomly assigned into one of three treatment groups: lamotrigine (100 to 400 mg/day), lithium (serum levels of 0.8 to 1.1 mMOL/L) or placebo for a maximum of 76 weeks (18 months). Treatment regimens were maintained until an emerging mood episode (depressive or manic) deemed it necessary to intervene with additional pharmacotherapy or electroconvulsive therapy (ECT).
The primary endpoint was "Time to Intervention for a Mood Episode (TIME)", where the interventions were either additional pharmacotherapy or ECT. This endpoint was analyzed using three methods of handling data from patients who were withdrawn prior to having an intervention. The p-values for these analyses ranged from 0.003 to 0.023. In supportive analyses of time to first depressive episode and time to first manic/hypomanic or mixed episode, the lamotrigine patients had longer times to first depressive episode than placebo patients (p=0.015), and the treatment difference with respect to time to manic or hypomanic or mixed episodes was not statistically significant.
In clinical trials, propensity to induce destabilization, mania or hypomania whilst on lamotrigine therapy was not significantly different to placebo.
Pharmacokinetics: Absorption: Lamotrigine is rapidly and completely absorbed from the gut with no significant first pass metabolism. Peak plasma concentration occurs approximately 2.5 hours after oral drug administration. Time to maximum concentration is slightly delayed after food but the extent of absorption is unaffected. The pharmacokinetics are linear up to 450 mg, the highest single dose tested. There is considerable inter- individual variation in steady state maximum concentrations but within an individual concentrations rarely vary.
Distribution: Binding to plasma protein is about 55%; it is very unlikely that displacement from plasma protein would result in toxicity.
The volume of distribution (Vd) is 0.92 to 1.22 l/kg.
Metabolism: UDP-glucuronyl transferases have been identified as the enzymes responsible for metabolism of lamotrigine. Lamotrigine induces its own metabolism to a modest extend depending on dose. However, there is no evidence that lamotrigine affects the pharmacokinetics of other AEDs and data suggest that interactions between lamotrigine and drugs metabolised by cytochrome P450 enzymes are unlikely to occur.
Elimination: The mean steady state clearance in healthy adults is 39 ± 14 ml/min. Clearance of lamotrigine is primarily metabolic with subsequent elimination of glucuronide-conjugated material in urine. Less than 10% is excreted unchanged in the urine. Only about 2% of drug-related material is excreted in faeces. Clearance and half life are independent of dose. The mean elimination half-life in healthy adults is 24 to 35 hours. In a study of subjects with Gilbert's Syndrome, mean apparent clearance was reduced by 32% compared with normal controls but the values are within the range for the general population.
The half-life of lamotrigine is greatly affected by concomitant medication. Mean half life is reduced to approximately 14 hours when given with glucuronidation-inducing drugs such as carbamazepine and phenytoin and is increased to a mean of approximately 70 hours when co- administered with valproate alone. (See Dosage & Administration.)
Special Population: Children: Clearance adjusted for bodyweight is higher in children than in adults with the highest values in children under five years. The half-life of lamotrigine is generally shorter in children than in adults with a mean value of approximately 7 hours when given with enzyme-inducing drugs such as carbamazepine and phenytoin and increasing to mean values of 45 to 50 hours when co-administered with valproate alone. (See Dosage & Administration.)
Elderly: Results of a population pharmacokinetic analysis including both young and elderly patients with epilepsy, enrolled in the same trials, indicated that the clearance of lamotrigine did not change to a clinically relevant extent. After single doses apparent clearance decreased by 12% from 35 ml/min at age 20 to 31 ml/min at 70 years. The decrease after 48 weeks of treatment was 10% from 41 to 37 ml/min between the young and the elderly groups. In addition, pharmacokinetics of lamotrigine was studied in 12 healthy elderly subjects following a 150 mg single dose. The mean clearance in the elderly (0.39 ml/min/kg) lies within the range of the mean clearance values (0.31 to 0.65 ml/min/kg) obtained in 9 studies with non-elderly adults after single doses of 30 to 450 mg.
Patients with renal impairment: Twelve volunteers with chronic renal failure, and another 6 individuals undergoing hemodialysis were each given a single 100 mg dose of lamotrigine. Mean CL/F were 0.42 ml/min/kg (chronic renal failure), 0.33 ml/min/kg (between hemodialysis), and 1.57 ml/min/kg (during hemodialysis) compared to 0.58 ml/min/kg in healthy volunteers. Mean plasma half-lives were 42.9 h (chronic renal failure), 57.4h (between hemodialysis) and 13.0h (during hemodialysis), compared to 26.2h in healthy volunteers. On average, approximately 20% (range=5.6 to 35.1) of the amount of lamotrigine present in the body was eliminated during a 4h hemodialysis session. For this patient population, initial doses of lamotrigine should be based on patients' AED regimen; reduced maintenance doses may be effective for patients with significant renal functional impairment.
Patients with hepatic impairment: A single-dose pharmacokinetic study was performed in 24 subjects with various degrees of hepatic impairment and 12 healthy subjects as controls. The median apparent clearance of lamotrigine was 0.31, 0.24 or 0.10 ml/min/kg in patients with grade A, B or C (Child-Pugh Classification) hepatic impairment, respectively, compared to 0.34 ml/min/kg in the healthy controls. Initial, escalation, and maintenance doses should generally be reduced by approximately 50% in patients with moderate (Child-Pugh Grade B) and 75% in patients with severe (Child-Pugh Grade C) hepatic impairment. Escalation and maintenance doses should be adjusted according to clinical response.
Toxicology: Preclinical Safety Data: Reproductive toxicology studies with lamotrigine in animals at doses in excess of the human therapeutic dosage showed no teratogenic effects. However, as lamotrigine is a weak inhibitor of dihydrofolate reductase, there is a theoretical risk of human foetal malformations when the mother is treated with a folate inhibitor during pregnancy. The results of a wide range of mutagenicity tests indicate that lamotrigine does not present a genetic risk to man. Lamotrigine was not carcinogenic in long-term studies in the rat and the mouse.
Indications/Uses
Epilepsy: Adults and children over 12 years of age: Adjunctive or monotherapy in the treatment of epilepsy, for partial seizures and generalized seizures including tonic-clonic seizures and the seizures associated with Lennox-Gastaut syndrome.
Children 2 to 12 years of age: Lamotrigine is indicated as adjunctive therapy in the treatment of epilepsy, for partial seizures and generalised seizures including tonic-clonic seizures and the seizuies associated with Lennox-Gastaut Syndrome.
Initial monotherapy treatment in newly diagnosed paediatric patients is not recommended.
After epileptic control has been achieved during adjunctive therapy, concomitant anti-epileptic drugs (AEDs) may be withdrawn and patients continued on lamotrigine monotherapy.
Bipolar Disorder: Adults 18 years of age and older: Lamotrix is indicated for the prevention of depressive episodes in patients with bipolar disorder. Safety and efficacy of lamotrigine in the acute treatment of mood episodes has not been established. The physician who elects to use lamotrigine for periods extending beyond 18 months should periodically re-evaluate the long-term usefulness of the drug for the individual patient.
Dosage/Direction for Use
Lamotrigine tablets should be swallowed whole and should not be chewed or crushed.
If a calculated dose of Lamotrix, e.g. for use in children (epilepsy only) or patients with hepatic impairment, cannot be divided into multiple lower strength tablets, the dose to be administered is that equal to the nearest lower strength of whole tablets.
It is strongly recommended that therapy with lamotrigine is initiated at the recommended doses. Careful incremental titration of the dose may decrease the severity of skin rashes. There are suggestions, yet to be proven, that the risk of severe, potentially life-threatening rash may be increased by co-administration of lamotrigine with valproate.
However, cases have been reported in the absence of these factors. Therefore, it is important that the dosing recommendations to be followed closely.
Restarting Therapy: Prescribers should assess the need for escalation to maintenance dose when restarting lamotrigine in patients who have discontinued lamotrigine for any reason, since the risk of serious rash is associated with high initial doses and exceeding the recommended dose escalation for lamotrigine (see Precautions). The greater the interval of time since the previous dose, the more consideration should be given to escalation to the maintenance dose. When the interval since discontinuing lamotrigine exceeds five half-lives (see Pharmacology: Pharmacokinetics under Actions), lamotrigine should generally be escalated to the maintenance dose according to the appropriate schedule.
It is recommended that lamotrigine not be restarted in patients who have discontinued due to rash associated with prior treatment with lamotrigine unless the potential benefit clearly outweighs the risk.
Epilepsy: When concomitant antiepileptic drugs are withdrawn to achieve lamotrigine monotherapy or other AEDs are added on to treatment regimes containing lamotrigine, consideration should be given to the effect this may have on lamotrigine pharmacokinetics (see Interactions).
Adults and children over 12 years of age (see Table 1): Dosage in epilepsy monotherapy: The initial LAMOTRIX dose in monotherapy is 25mg once a day for two weeks, followed by 50mg once a day for two weeks. Thereafter, the dose should be increased by a maximum of 50mg-100mg every 1-2 weeks until the optimal response is achieved. The usual maintenance dose to achieve optimal response is 100 - 200 mg/day given once a day or as two divided doses. Some patients have required 500mg/day of lamotrigine to achieve the desired response.
Because of a risk of rash the initial dose and the subsequent dose escalation should not be exceeded (see Precautions).
Dosage in epilepsy add-on therapy: In patients taking valproate with / without any other anti-epileptic drug (AED) the initial LAMOTRIX dose is 25mg every alternate day for two weeks, followed by 25mg once a day for two weeks. Thereafter, the dose should be increased by a maximum of 25-50mg every 1 - 2 weeks until the optimal response is achieved. The usual maintenance dose to achieve optimal response is 100 - 200mg/day given once a day or in two divided doses. In those patients taking concomitant AEDs or other medications (see Interactions) that induce lamotrigine glucuronidation with/without other AEDs (except valproate), the initial LAMOTRIX dose is 50 mg once a day for two weeks, followed by 100 mg/day given in two divided doses for two weeks. Thereafter, the dose should be increased by a maximum of 100mg every 1-2 weeks until the optimal response is achieved. The usual maintenance dose to achieve optimal response is 200-400 mg/day given in two divided doses. Some patients have required 700 mg/day of lamotrigine to achieve the desired response.
In those patients taking other medications that do not significantly inhibit or induce lamotrigine glucuronidation (see Interactions), the initial Lamotrix dose is 25 mg once a day for two weeks, followed by 50 mg once a day for two weeks. Thereafter, the dose should be increased by a maximum of 50 to 100 mg every one to two weeks until the optimal response is achieved. The usual maintenance dose to achieve an optimal response is 100 to 200 mg/day given once a day or as two divided doses. (See Table 1.)

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Because of a risk of rash the initial dose and subsequent dose escalation should not be exceeded (see Precautions).
Children aged 2 to 12 years: In patients taking valproate with/without any other anti-epileptic drug (AED), the initial Lamotrix dose is 0.15mg/kg bodyweight/day given once a day for two weeks, followed by 0.3mg/kg/day given once a day for two weeks. Thereafter, the dose should be increased by a maximum of 0.3mg/kg every 1-2 weeks until the optimal response is achieved. The usual maintenance dose to achieve optimal response is 1-5 mg/kg/day given once a day or in two divided doses, with a maximum of 200 mg/day.
In those patients taking concomitant AEDs or other medications (see Interactions) that induce lamotrigine glucuronidation with/without other AEDs (except valproate) the initial lamotrigine dose is 0.6 mg/kg bodyweight/day given in two divided doses for two weeks, followed by 1.2 mg/kg/day given in two divided doses for two weeks. Thereafter, the dose should be increased by a maximum of 1.2mg/kg every 1-2 weeks until the optimal response is achieved. The usual maintenance dose to achieve optimal response is 5-15 mg/kg/day given in two divided doses, with a maximum of 400 mg/day.
To ensure a therapeutic dose is maintained the weight of a child must be monitored and the dose reviewed as weight changes occur. (See Table 2.)

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Because of the risk of rash the initial dose and subsequent dose escalation should not be exceeded (see Precautions).
It is likely that patients aged 2-6 years will require a maintenance dose at the higher end of the recommended range.
Children aged less than two years: Lamotrigine has not been studied as monotherapy in children less than 2 years of age or as add-on therapy in children less than 1 month of age. The safety and efficacy of lamotrigine as add on therapy of partial seizures in children aged 1 month to 2 years has not been established (see Pharmacology: Pharmacodynamics: Clinical Studies under Actions). Therefore LAMOTRIX is not recommended in children less than 2 years of age.
Bipolar Disorder: Adults (18 years of age and over): Because of the risk of rash the initial dose and subsequent dose escalation should not be exceeded (see Precautions).
LAMOTRIX is recommended for use in bipolar patients at risk for a future depressive episode. The following transition regimen should be followed to prevent recurrence of depressive episodes. The transition regimen involves escalating the dose of LAMOTRIX to a maintenance stabilization dose over six weeks (see Table 3) after which other psychotropic and/or anti-epileptic drugs can be withdrawn, if clinically indicated (see Table 4). Adjunctive therapy should be considered for the prevention of manic episodes, as efficacy with lamotrigne in mania has not been conclusively established. There is no evidence of an increased risk of mania, hypomania or mixed type episodes with lamotrigine treatment compared to placebo. (See Table 3.)

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Adjunct therapy with inhibitors of lamotrigine glucuronidation e.g. valproate: In patients taking glucuronidation inhibiting concomitant drugs such as valproate the initial LAMOTRIX dose is 25mg every alternate day for two weeks, followed by 25mg once a day for two weeks. The dose should be increased to 50mg once a day (or in two divided doses) in week 5. The usual target dose to achieve optimal response is 100mg/day given once a day or in two divided doses. However, the dose can be increased to a maximum daily dose of 200mg, depending on clinical response.
Adjunct therapy with inducers of lamotrigine glucuronidation in patients NOT taking inhibitors such as Valproate. This dosage regimen should be used with: Phenytoin, Carbamazepine, Phenobarbitone, Primidone or with others inducers of lamotrigine glucuronidation (see Interactions).
In those patients currently taking drugs that induce lamotrigine glucuronidation and not taking Valproate, the initial LAMOTRIX dose is 50mg once a day for two weeks, followed by 100mg/day given in two divided doses for two weeks. The dose should be increased to 200mg/day given as two divided doses in week 5. The dose may be increased in week 6 to 300mg/day however, the usual target dose to achieve optimal response is 400mg/day given in two divided doses which may be given from week 7.
Monotherapy with LAMOTRIX or Adjunctive therapy in patients taking other medications that do not significantly inhibit or induce lamotrigine glucuronidation (see Interactions): The initial Lamotrix dose is 25mg once a day for two weeks, followed by 50mg once a day (or in two divided doses) for two weeks. The dose should be increased to 100mg/day in week 5. The usual target dose to achieve optimal response is 200mg/day given once a day or as two divided doses. However, a range of 100 to 400mg was used in clinical trials. Once the target daily maintenance stabilization dose has been achieved, other psychotropic medications may be withdrawn as laid out in the dosage schedule as follows (see Table 4).

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Following withdrawal of adjunct therapy with inhibitors of lamotrigine glucuronidation e.g. Valproate: The dose of Lamotrix should be increased to double the original target stabilisation dose and maintained at this, once Valproate has been terminated.
Following withdrawal of adjunct therapy with inducers of lamotrigine glucuronidation depending on original maintenance dose. This dosage regimen should be used with: Phenytoin, Carbamazepine, Phenobarbitone, Primidone or with others drugs known to induce of lamotrigine glucuronidation (see Interactions). The dose of LAMOTRIX should be gradually reduced over three weeks as the glucuronidation inducer is withdrawn.
Following withdrawal of adjunct therapy with medications that do not significantly inhibit or induce lamotrigine glucuronidation (see Interactions): The target dose achieved in the dose escalation programme should be maintained throughout withdrawal of the other medication.
Adjustment of LAMOTRIX daily dosing in patients with BIPOLAR DISORDER following addition of other medications: There is no clinical experience in adjusting the lamotrigine daily dose following the addition of other medications. However, based on drug interaction studies, the following recommendations can be made (see Table 5, as follows): (See Table 5.)

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Discontinuation of LAMOTRIX in adult patients with BIPOLAR DISORDER: In clinical trials, there was no increase in the incidence, severity or type of adverse experiences, following abrupt termination of lamotrigine versus placebo. Therefore patients may terminate LAMOTRIX without a step-wise reduction of dose.
Children and adolescents (less than 18 years of age): LAMOTRIX is not indicated for use in bipolar disorder in children and adolescents aged less than 18 years old (see Precautions). Safety and efficacy of lamotrigine in bipolar disorder has not been evaluated in this age group. Therefore, a dosage recommendation cannot be made.
General dosing recommendations for lamotrix in special patient populations: Women taking hormonal contraceptives: Starting LAMOTRIX in patients already taking hormonal contraceptives: Although an oral contraceptive has been shown to increase the clearance of lamotrigine (see Precautions and Interactions), no adjustments to the recommended dose escalation guidelines for LAMOTRIX should be necessary solely based on the use of hormonal contraceptives. Dose escalation should follow the recommended guidelines based on whether lamotrigine is added to an inhibitor of lamotrigine glucuronidation e.g. valproate; whether Lamotrix is added to an inducer of lamotrigine glucuronidation e.g. carbamazepine, Phenytoin, phenobarbital, primidone, rifampin or lopinavir/ritonavir; or whether LAMOTRIX is added in the absence of valproate, carbamazepine, phenytoin, phenobarbital, primidone, rifampicin or lopinavir/ritonavir (see Table 1 for epilepsy and Table 3 for bipolar disorder patients).
Starting hormonal contraceptives in patients already taking maintenance doses of lamotrigine and NOT taking inducers of lamotrigine glucuronidation:The maintenance dose of lamotrigine may need to be increased as much as two-fold (see Precautions & Interactions). It is recommended that from the time that the hormonal contraceptive is started, the lamotrigine dose is increased by 50 to 100 mg/day every week, according to the individual clinical response. Dose increases should not exceed this rate, unless the clinical response supports larger increases.
Stopping hormonal contraceptives in patients already taking maintenance doses of LAMOTRIX and NOT taking inducers of lamotrigine glucuronidation: The maintenance dose of lamotrigine will in most cases need to be decreased as much as 50% (see Precautions & Interactions). It is recommended to gradually decrease the daily dose of lamotrigine by 50 to 100 mg each week (at a rate not exceeding 25% of the total daily dose per week) over a period of 3 weeks, unless the clinical response indicates otherwise.
Elderly (over 65 years of age): No dosage adjustment from recommended schedule is required. The pharmacokinetics of lamotrigine in this age group do not differ significantly from a non-elderly adult population. As older patients are more likely to suffer from intercurrent illness and require medications to treat other medical conditions, lamotrigine should be used cautiously in these patients and they should be monitored regularly.
Hepatic impairment: Initial, escalation and maintenance doses should generally be reduced by approximately 50% in patients with moderate (Child-Pugh grade B) and 75% in severe (Child-Pugh grade C) hepatic impairment.
Escalation and maintenance doses should be adjusted according to clinical response (see Pharmacology: Pharmacokinetics under Actions).
Renal impairment: Caution should be exercised when administering LAMOTRIX to patients with renal failure. For patients with end-stage renal failure, initial doses of LAMOTRIX should be based on patients' AEDs regimen; reduced maintenance doses may be effective for patients with significant renal functional impairment (see Precautions). For more detailed pharmacokinetic information see Pharmacology: Pharmacokinetics under Actions.
Overdosage
Acute ingestion of doses in excess of 10 to 20 times the maximum therapeutic dose have been reported, including fatal ones. Overdose has resulted in symptoms including nystagmus, ataxia, impaired consciousness, grand mal convulsion and coma. QRS broadening (intraventricular conduction delay) has also been observed in overdose patients.
In the event of overdosage, the patient should be admitted to hospital and given appropriate supportive therapy as clinically indicated or as recommended by the national poisons centre, where available.
Contraindications
Lamotrix is contraindicated in patients with known hypersensitivity to lamotrigine, or to any of the other constituents of the tablets.
Special Precautions
Haemophagocytic lymphohistiocytosis (HLH): HLH has occurred in patients taking lamotrigine. HLH is a syndrome of pathological immune activation, which can be life threatening, characterised by clinical signs and symptoms such as fever, rash, neurological symptoms, hepatosplenomegaly, lymphadenopathy, cytopenias, high serum ferritin, hypertriglyceridaemia and abnormalities of liver function and coagulation. Symptoms occur generally within 4 weeks of treatment initiation. Immediately evaluate patients who develop these signs and symptoms and consider a diagnosis of HLH. Lamotrigine should be discontinued unless an alternative aetiology can be established.
Skin rash: There have been reports of adverse skin reactions, which have generally occurred within the first eight weeks after initiation of Lamotrigine treatment. The majority of rashes are mild and self limiting, however, serious rashes requiring hospitalization and discontinuation of lamotrigine have also been reported. These have included potentially life threatening rashes such as Stevens Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) (see Adverse Reactions). It is not possible to predict reliably which rashes will prove to be life-threatening. Accordingly, lamotrigine should ordinarily be discontinued at the first sign of rash, unless the rash is clearly not drug related. Discontinuation of treatment may not prevent a rash from becoming life-threatening or permanently disabling or disfiguring.
In adults enrolled in studies utilizing the current lamotrigine dosing recommendations the incidence of serious skin rashes is approximately 1 in 500 in epilepsy patients. Approximately half of these cases have been reported as SJS (1 in 1000).
In clinical trials in patients with bipolar disorder, the incidence of serious skin rashes is approximately 1 in 1000. The risk of serious skin rashes in children is higher than in adults. Available data from a number of studies suggest the incidence of rashes associated with hospitalization in epileptic children is from 1 in 300 to 1 in 100.
In children, the initial presentation of a rash can be mistaken for an infection. Physicians should consider the possibility of a drug reaction in children that develop symptoms of rash and fever during the first 8 weeks of therapy.
Additionally the overall risk of rash appears to be strongly associated with: high initial doses of lamotrigine and exceeding the recommended dose escalation of lamotrigine therapy (see Dosage & Administration); concomitant use of valproate (see Dosage & Administration).
Caution is also required when treating patients with a history of allergy or rash to other antiepileptic drugs as it was found in two studies (n =767 and n=988) on the frequency of rash after treatment with lamotrigine that the rate of rash was approximately three to four times higher in patients with such history than without.
All patients (adults and children) who develop a rash should be promptly evaluated and lamotrigine withdrawn immediately unless the rash is clearly not drug related. It is recommended that lamotrigine not be restarted in patients who have discontinued due to rash associated with prior treatment with lamotrigine unless the potential benefit clearly outweighs the risk.
Rash has also been reported as part of a hypersensitivity syndrome associated with a variable pattern of systemic symptoms including fever, lymphadenopathy, facial oedema and abnormalities of the blood and liver and aseptic meningitis (see Adverse Reactions). The syndrome shows a wide spectrum of clinical severity and may, rarely, lead to Disseminated Intravascular Coagulation (DIC) and multiorgan failure. It is important to note that early manifestations of hypersensitivity (e.g. fever and lymphadenopathy) may be present even though rash is not evident. If such signs and symptoms are present the patient should be evaluated immediately and lamotrigine discontinued if an alternative aetiology cannot be established.
Aseptic Meningitis: Therapy with LAMOTRIX increases the risk of developing aseptic meningitis. Because of the potential for serious outcomes of untreated meningitis due to other causes, patients should also be evaluated for other causes of meningitis and treated as appropriate.
Post-marketing cases of aseptic meningitis have been reported in paediatric and adult patients taking LAMOTRIX for various indications. Symptoms upon presentation have included headache, fever, nausea, vomiting and nuchal rigidity. Rash, photophobia, myalgia, chills, altered consciousness and somnolence were also noted in some cases. Symptoms have been reported to occur within 1 day to one and a half months following the initiation of treatment. In most cases, symptoms were reported to resolve after discontinuation of LAMOTRIX. Re-exposure resulted in a rapid return of symptoms (from 30 minutes to 1 day following re-initiation of treatment) that were frequently more severe. Lamotrigine should not be restarted in patients who have discontinued due to aseptic meningitis associated with prior treatment of lamotrigine.
Some of the patients treated with LAMOTRIX who developed aseptic meningitis had underlying diagnoses of systemic lupus erythematosus or other autoimmune diseases.
Cerebrospinal fluid (CSF) analysed at the time of clinical presentation in reported cases was characterised by a mild to moderate pleocytosis, normal glucose levels and mild to moderate increase in protein. CSF white blood cell count differentials showed a predominance of neutrophils in a majority of the cases, although a predominance of lymphocytes was reported in approximately one-third of the cases. Some patients also had new onset of signs and symptoms of involvement of other organs (predominantly hepatic and renal involvement), which may suggest that in these cases the aseptic meningitis observed was part of a hypersensitivity reaction.
Suicide risk: Symptoms of depression and/or bipolar disorder may occur in patients with epilepsy, and there is evidence that patients with epilepsy and bipolar disorder have an elevated risk for suicidality. Twenty-five to 50% of patients with bipolar disorder attempt suicide at least once, and may experience worsening of their depressive symptoms and/or the emergence of suicidal ideation and behaviours (suicidality) whether or not they are taking medications for bipolar disorder, including LAMOTRIX.
Suicidal ideation and behaviour have been reported in patients treated with AEDs in several indications, including epilepsy and bipolar disorder. A meta-analysis of randomised placebo-controlled trials of AEDs (including lamotrigine) has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for lamotrigine.
Therefore patients should be monitored for signs of suicidal ideation and behaviours.
Patients (and caregivers of patients) should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge.
Clinical worsening in bipolar disorder: Patients receiving LAMOTRIX for bipolar disorder should be closely monitored for clinical worsening (including development of new symptoms) and suicidality, especially at the beginning of a course of treatment, or at the time of dose changes. Certain patients, such as those with a history of suicidal behaviour or thoughts, young adults, and those patients exhibiting a significant degree of suicidal ideation prior to commencement of treatment, may be at a greater risk of suicidal thoughts or suicide attempts, and should receive careful monitoring during treatment.
Patients (and caregivers of patients) should be alerted about the need to monitor for any worsening of their condition (including development of new symptoms) and/or the emergence of suicidal ideation/behaviour or thoughts of harming themselves and to seek medical advice immediately if these symptoms present.
Consideration should be given to changing the therapeutic regimen, including possibly discontinuing the medication, in patients who experience clinical worsening (including development of new symptoms) and/or the emergence of suicidal ideation/behaviour, especially if these symptoms are severe, abrupt in onset, or were not part of the patient's presenting symptoms.
Hormonal contraceptives: Effect of hormonal contraceptives on LAMOTRIX efficacy: An ethinyloestradiol/levonorgestrel (30 mcg/150 mcg) combination has been demonstrated to increase the clearance of lamotrigine by approximately two-fold resulting in decreased lamotrigine levels (see Interactions). Following titration, higher maintenance doses of lamotrigine (by as much as two fold) will be needed in most cases to attain a maximal therapeutic response. In women not already taking an inducer of lamotrigine glucuronidation and taking a hormonal contraceptive that includes one week of inactive medication (e.g. "pill-free week"), gradual transient increases in lamotrigine levels will occur during the week of inactive medication. These increases will be greater when lamotrigine dose increases are made in the days before or during the week of inactive medication. For dosing instructions see "General Dosing Recommendations for LAMOTRIX in Special Patient Populations, under Dosage & Administration" Clinicians should exercise appropriate clinical management of women starting or stopping hormonal contraceptives during lamotrigine therapy and lamotrigine dosing adjustments will be needed in most cases. Effects of other hormonal contraceptive preparations or HRT on LAMOTRIX: Other oral contraceptive and hormone replacement therapy (HRT) treatments have not been studied, though they may similarly affect lamotrigine pharmacokinetic parameters.
Effects of lamotrigine on hormonal contraceptive efficacy: An interaction study in 16 healthy volunteers has shown that when lamotrigine and a hormonal contraceptive (ethinyloestradiol/levonorgestrel combination) are administered in combination, there is a modest increase in levonorgestrel clearance and changes in serum FSH and LH (see Interactions). The impact of these changes on ovarian ovulatory activity is unknown. However, the possibility of these changes resulting in decreased contraceptive efficacy insome patients taking hormonal preparations with lamotrigine cannot be excluded. A limited number of reports have been received of unexpected pregnancies and of menstrual bleeding disorders (e.g. break through bleeding) occurring with the concomitant use of lamotrigine and hormonal contraceptives. Therefore patients should be instructed to promptly report changes in their menstrual pattern, i.e., breakthrough bleeding while receiving lamotrigine in combination with these medications.
Effect of lamotrigine on organic cationic transporter 2 (OCT 2) substrates: Lamotrigine is an inhibitor of renal tubular secretion via OCT 2 proteins (see Interactions). This may result in increased plasma levels of certain drugs that are substantially excreted via this route. Co-administration of LAMOTRIX with OCT 2 substrates with a narrow therapeutic index e.g. dofetilide is not recommended.
Acute Multiorgan Failure: Multiorgan failure, which in some cases has been fatal or irreversible, has been observed in patients receiving lamotrigine. Fatalities associated with mutiorgan failure and various degrees of hepatic failure have been reported in 2 of 3,796 adult patients and 4 of 2,435 paediatric patients who received lamotrigine in clinical trials. No such fatalities have been reported in bipolar patients in clinical trials. Rare fatalities from multiorgan failure have also been reported in compassionate plea and postmarketing use. The majority of these deaths occurred in association with other serious medical events, including status epilepticus and overwhelming sepsis, and hantavirus making it difficult to identify the initial cause. Additionally, 3 patients (a 45-year-old woman, a 3.5-year-old boy, and an 11-year-old girl) developed multiorgan dysfunction and disseminated intravascular coagulation 9 to 14 days after lamotrigine was added to their AED regimens. Rash and elevated transaminases were also present in all patients and rhabdomyolysis was noted in two patients. Both paediatric patients were receiving concomitant therapy with valproate, while the adult patient was being treated with carbamazepine and clonazepam. All patients subsequently recovered with supportive care after treatment with lamotrigine was discontinued.
Binding in the Eye and Other Melanin-Containing Tissues: Because lamotrigine binds to melanin, it could accumulate in melanin-rich tissues over time. This raises the possibility that lamotrigine may cause toxicity in these tissues after extended use. Although ophthalmological testing was performed in one controlled clinical trial, the testing was inadequate to exclude subtle effects or injury occurring after long-term exposure. Moreover, the capacity of available tests to detect potentially adverse consequences, if any, of lamotrigine's binding to melanin is unknown. Accordingly, although there are no specific recommendations for periodic ophthalmological monitoring, prescribers should be aware of the possibility of long-term ophthalmologic effects.
Dihydrofolate Reductase:Lamotrigine is a weak inhibitor of dihydrofolate reductase, hence there is a possibility of interference with folate metabolism during long-term therapy. However, during prolonged human dosing, lamotrigine did not induce significant changes in the haemoglobin concentration, mean corpuscular volume, or serum or red blood cell folate concentrations up to 1 year or red blood cell folate concentrations for up to 5 years.
Renal Failure: In single dose studies in subjects with end stage renal failure, plasma concentrations of lamotrigine were not significantly altered. However, accumulation of the glucuronide metabolite is to be expected; caution should therefore be exercised in treating patients with renal failure.
Patients taking other preparations containing lamotrigine: LAMOTRIX tablets should not administered to patients currently being treated with other preparation containing lamotrigine without consulting a doctor.
Brugada-type ECG: A very rare association with Brugada-type ECG has been observed, although a causal relationship has not been established. Therefore, careful consideration should be given before using LAMOTRIX in patients with Brugada syndrome.
Epilepsy: As with other AEDs, abrupt withdrawal of LAMOTRIX may provoke rebound seizures. Unless safety concerns (for example rash) require an abrupt withdrawal, the dose of lamotrigine should be gradually decreased over a period of 2 weeks.
There are reports in the literature that severe convulsive seizures including status epilepticus may lead to rhabdomyolysis, multiorgan dysfunction and disseminated intravascular coagulation (DIC), sometimes with fatal outcome. Similar cases have occurred in association with the use of lamotrigine.
Bipolar Disorder: Children and adolescents (less than 18 years of age): Treatment with antidepressants is associated with an increased risk of suicidal thinking and behaviour in children and adolescents with major depressive disorder and other psychiatric disorders.
Effects on Ability to Drive and Use Machines: Two volunteer studies have demonstrated that the effect of lamotrigine on fine visual motor co-ordination, eye-movements, body sway and subjective sedative effects did not differ from placebo. In clinical trials with lamotrigine adverse events of neurological character such as dizzines and diplopia have been reported. Therefore, patients should see how lamotrigine therapy affects them before driving or operating machinery.
Epilepsy: as there is individual variation in response to all antiepileptic drug therapy patient should consult their physician on the specific issues of driving and epilepsy.
Use In Pregnancy & Lactation
Pregnancy: Administration of lamotrigine did not impair fertility in animal reproductive studies.
There is no experience of the effect of lamotrigine on human fertility.
Postmarketing data from several prospective pregnancy registries have documented outcomes in over 8,700 women exposed to lamotrigine monotherapy during the first trimester of pregnancy. These data do not exclude an increased risk for major congenital malformations. Although a number of registries have reported an increase in the risk of isolated oral cleft malformations, a completed case control study with 259 exposures to lamotrigine therapy did not demonstrate an increased risk of oral clefts compared to other major congenital malformations following exposure to lamotrigine. Animal studies have shown developmental toxicity. The data on use of lamotrigine in polytherapy combination are insufficient to assess whether the risk of malformations associated with other agents is affected by concomitant lamotrigine use.
As with other medicines, LAMOTRIX should only be used during pregnancy if the expected benefits outweigh the potential risks.
Physiological changes during pregnancy may affect lamotrigine levels and/or therapeutic effect. There have been reports of decreased lamotrigine levels during pregnancy. Appropriate clinical management of pregnant women during LAMOTRIX therapy should be ensured.
Lamotrigine has been reported to pass into breast milk in highly variable concentrations, resulting in total lamotrigine levels in infants of up to approximately 50% of the mother's. Therefore, in some breastfed infants, serum concentrations of lamotrigine may reach levels at which pharmacological effects occur.
The potential benefits of breast feeding should be weighed against the potential risk of adverse effects occurring in the infant.
Adverse Reactions
The adverse reactions identified from epilepsy or bipolar disorder clinical trial data have been divided into indication specific sections. Additional adverse reactions identified through post-marketing surveillance for both indications are included in as follows. All three sections should be consulted when considering the overall safety profile of LAMOTRIX.
The following convention has been used utilised for the classification of undesirable effects: Very common (≥ 1/10), Common (≥ 1/100 to < 1/10), Uncommon (≥ 1/1000 to < 1/100), Rare (≥ 1/10,000 to < 1/1000), Very rare (< 1/10,000).
Epilepsy: The following adverse reactions were identified during epilepsy clinical trials and should be considered alongside those seen in the bipolar disorder clinical trials and post- marketing sections for an overall safety profile of lamotrigine.
Skin and subcutaneous tissue disorders:
Very common: Skin rash; Rare: Stevens Johnson syndrome; Very rare: Toxic epidermal necrolysis.
In a double-blind, add-on clinical trials in adults, skin rashes occurred in up to 10% of patients taking lamotrigine and in 5% of patients taking placebo. The skin rashes led to the withdrawal of lamotrigine treatment in 2% of patients. The rash, usually maculopapular in appearance, generally appears within eight weeks of starting treatment and resolves on withdrawal of lamotrigine (see Precautions).
Rarely, serious potentially life threatening skin rashes, including Stevens Johnson syndrome and toxic epidermal necrolysis (Lyell's Syndrome) have been reported. Although the majority recovers on drug withdrawal, some patients experience irreversible scarring and there have been rare cases of associated death (see Precautions). The overall risk of rash, appears to be strongly associated with: high initial doses of lamotrigine and exceeding the recommended dose escalation of lamotrigine therapy (see Dosage & Administration); concomitant use with valproate (see Dosage & Administration). Rash has also been reported as part of a hypersensitivity syndrome associated with a variable pattern of systemic symptoms (see Immune system disorders**).
Blood and lymphatic system disorders: Very rare: Haematological abnormalities including neutropenia, leucopenia, anemia, thrombocytopenia, pancytopenia, aplastic anaemia and agranulocytosis. Frequency not known: Lymphadenopathy; Haematological abnormalities may or may not be associated with the hypersensitivity syndrome (see Immune system disorders**).
Immune system disorders: Very rare: Hypersensitivity syndrome** (including such symptoms as fever, lymphadenopathy, facial oedema, abnormalities of the blood and liver, disseminated intravascular coagulation (DIC), multi-organ failure.
** Rash has also been reported as part of a hypersensitivity syndrome associated with a variable pattern of systemic symptoms including fever, lymphadenopathy, facial oedema, abnormalities of the blood and liver. The syndrome shows a wide spectrum of clinical severity and may, rarely, lead to disseminated intravascular coagulation (DIC) and multiorgan failure. It is important to note that early manifestations of hypersensitivity (e.g. fever, lymphadenopathy) may be present even though rash is not evident. If such signs or symptoms are present, the patient should be evaluated immediately and LAMOTRIX discontinued if an alternative aetiology cannot be established.
Psychiatric disorders: Common: Aggression, Irritability; Very rarely: Tics, hallucinations, confusion.
Nervous system disorders: Very common: Headache; Common: Somnolence, insomnia, dizziness, tremor; Uncommon: Ataxia; Rare: Nystagmus.
Eye disorders: Uncommon: Diplopia, blurred vision.
Gastrointestinal disorders: Common: Nausea, vomiting, diarrhoea.
Hepato-billiary disorders: Very rare: Increased liver function tests, hepatic dysfunction, hepatic failure; Hepatic dysfunction usually occurs in association with hypersensitivity reactions but isolated cases have been reported without overt signs of hypersensitivity.
Musculo-skeletal and connective tissue disorders: Very rare: Lupus-like reactions.
General disorders and administration site conditions: Common: Tiredness.
Bipolar Disorder: The following adverse reactions were identified during bipolar disorder clinical trials and should be considered alongside those seen in epilepsy clinical trials and post-marketing sections for an overall safety profile of lamotrigine.
Skin and subcutaneous tissue disorders: Very common: Skin rash; Rare: Stevens Johnson syndrome; When all bipolar disorder studies (controlled and uncontrolled) conducted with lamotrigine are considered, skin rashes occurred in 12% of patients on lamotrigine. Whereas, in controlled clinical trials with bipolar disorder patients, skin rashes occurred in 8% of patients taking lamotrigine and in 6% of patients taking placebo.
Nervous system disorders: Very common: Headache; Common: Agitation, somnolence, dizziness.
Musculo-skeletal and connective tissue disorders: Common: Arthralgia.
General disorders and administration site conditions:
Common: Pain, backpain.
Post-Marketing: This section includes adverse reactions identified through post-marketing surveillance for both indications. These adverse reactions should be considered alongside those seen in the epilepsy and bipolar disorder clinical trials sections for an overall safety profile of lamotrigine.
Blood and lymphatic system disorders: Very rare: Haemophagocytic lymphohistiocytosis (see Precautions).
Skin and subcutaneous tissue disorders: Rare: Alopecia.
Psychiatric disorders: Very rare: Nightmares.
Nervous system disorders: Very common: Somnolence, ataxia, headache, dizziness; Common: Nystagmus, tremor, insomnia; Rare: Aseptic meningitis (see Precautions); Very rare: Agitation, unsteadiness, movement disorders, worsening of Parkinson's disease, extrapyramidal effects, choreoathetosis.
There have been reports that lamotrigine may worsen parkinsonian symptoms in patients with pre-existing Parkinson's disease, and isolated reports of extrapyramidal effects and choreoathetosis in patients without this underlying condition.
Eye disorders Very common: Diplopia, blurred vision; Rare: Conjunctivitis.
Gastrointestinal disorders; Very common: Nausea, vomiting. Common: Diarrhoea.
Epilepsy only: Nervous system disorders: Very rare: Increase in seizure frequency.
Drug Interactions
Uridine 5'-diphospho (UDP) glucuronyl transferases (UGTs) have been identified as the enzymes responsible for metabolism of lamotrigine. Drugs that induce or inhibit glucuronidation may, therefore, affect the apparent clearance of lamotrigine. Strong or moderate inducers of the cytochrome P450 3A4 (CYP3A4) enzyme, which are also known to induce UGTs, may also enhance the metabolism of lamotrigine. Those drugs that have been demonstrated to have a clinically significant impact on lamotrigine metabolism are outlined in Table 6. Specific dosing guidance for these drugs is provided in Dosage & Administration There is no evidence that lamotrigine causes clinically significant induction or inhibition of cytochrome P450 enzymes. Lamotrigine may induce its own metabolism but the effect is modest and unlikely to have significant clinical consequences. (See Table 6.)

Click on icon to see table/diagram/image

Interactions involving AEDs (see Dosage & Administration):Valproate, which inhibits the glucuronidation of lamotrigine, reduces the metabolism of lamotrigine and increases the mean half life of lamotrigine nearly two fold. (See Precautions and Dosage & Administration.) Certain antiepileptic agents (such as phenytoin, carbamazepine, phenobarbitone and primidone) which induce cytochrome P450 enzymes also induce UGTs and therefore enhance the metabolism of lamotrigine. Other drug-classes which induce hepatic drug-metabolising enzymes may also enhance the metabolism of lamotrigine.
There have been reports of central nervous system events including dizziness, ataxia, diplopia, blurred vision and nausea in patients taking carbamazepine following the introduction of lamotrigine. These events usually resolve when the dose of carbamazepine is reduced. A similar effect was seen during a study of lamotrigine and oxcarbazepine in healthy adult volunteers, but dose reduction was not investigated.
In a study of healthy adult volunteers using doses of 200 mg lamotrigine and 1200 mg oxcarbazepine, oxcarbazepine did not alter the metabolism of lamotrigine and lamotrigine did not alter the metabolism of oxcarbazepine. The pharmacokinetic interaction between lamotrigine and oxcarbazepine in children has not been studied.
In a study in healthy volunteers, coadministration of felbamate (1,200 mg twice daily) with lamotrigine (100 mg twice daily for 10 days) appeared to have no clinically relevant effects on the pharmacokinetics of lamotrigine. Based on a retrospective analysis of plasma levels in patients who received lamotrigine both with and without gabapentin, gabapentin does not appear to change the apparent clearance of lamotrigine.
Potential drug interactions between levetiracetam and lamotrigine were assessed by evaluating serum concentrations of both agents during placebo-controlled clinical trials. These data indicate that lamotrigine does not influence the pharmacokinetics of levetiracetam and that levetiracetam does not influence the pharmacokinetics of lamotrigine. Steady-state trough plasma concentrations of lamotrigine were not affected by concomitant pregabalin (200 mg 3 times daily) administration. There are no pharmacokinetic interactions between lamotrigine and pregabalin. Topiramate resulted in no change in plasma concentrations of lamotrigine. Administration of lamotrigine resulted in a 15% increase in topiramate concentrations. In a study of patients with epilepsy, co-administration of zonisamide (200 to 400 mg/day) with lamotrigine (150 to 500 mg/day) for 35 days had no significant effect on the pharmacokinetics of lamotrigine. Plasma concentrations of lamotrigine were not affected by concomitant lacosamine (200, 400 or 600 mg/day) in placebo-controlled clinical trials in patients with partial-onset seizures.
In a pooled analysis of data from three placebo-controlled clinical trials investigating adjunctive perampanel in patients with partial-onset and primary generalised tonic-clonic seizures, the highest perampanel dose evaluated (12 mg/day) increased lamotrigine clearance by less than 10%. An effect of this magnitude is not considered to be clinical relevant. Although changes in the plasma concentrations of other antiepileptic drugs have been reported, controlled studies have shown no evidence that lamotrigine affects the plasma concentrations of concomitant antiepileptic drugs. Evidence from in-vitro studies indicates that lamotrigine does not displace other antiepileptic drugs from protein binding sites.
Interactions involving other psychoactive agents (see Dosage & Administration):The pharmacokinetic of lithium after 2g of anhydrous lithium gluconate given twice daily for six days to 20 healthy subjects were not altered by co-administration of 100 mg/day lamotrigine.
Multiple oral doses of bupropion had no statistically significant effects on the single dose pharmacokinetics of lamotrigine in 12 subjects and had only a slight increase in the AUC of lamotrigine glucuronide.
In a study in healthy adult volunteers, 15 mg olanzapine reduced the AUC and Cmax of lamotrigine by an average of 24% and 20%, respectively. An effect on this magnitude is not generally expected to be clinically relevant. Lamotrigine at 200 mg did not affect the pharmacokinetics of olanzapine.
Multiple oral doses of lamotrigine 400 mg daily had no clinically significant effect on the single dose pharmacokinetics of 2 mg risperidone in 14 healthy adult volunteers. Following the co-administration of risperidone 2 mg with lamotrigine, 12 out of the 14 volunteers reported somnolence compared to 1 out of 20 when risperidone was given alone, and none when lamotrigine was administered alone. In a study of 18 adult patients with bipolar I disorder, receiving an established regimen of lamotrigine (>/=100 mg/day), doses of aripiprazole were increased from 10 mg/day to a target of 30 mg/day over a 7 day period and continued once daily for a further 7 days. An average reduction of approximately 10% in Cmax and AUC of lamotrigine was observed. An effect of this magnitude is not expected to be of clinical consequence.
In vitro inhibition experiments indicated that the formation of lamotrigine's primary metabolite, the 2-N-glucuronide, was minimally affected by co-incubation with amitriptyline, bupropion, clonazepam, fluoxetine, haloperidol, or lorazepam. Bufuralol metabolism data from human liver microsome suggested that lamotrigine does not reduce the clearance of drugs eliminated predominantly by CYP2D6. Results of in vitro experiments also suggest that clearance of lamotrigine is unlikely to be affected by clozapine, phenelzine, risperidone, sertraline or trazodone.
Interactions involving hormonal contraceptives: Effect of hormonal contraceptives on lamotrigine pharmacokinetics: In a study of 16 female volunteers, 30 mcg ethinyloestradiol/150mcg levonorgestrel in a combined oral contraceptive pill caused an approximately two-fold increase in lamotrigine oral clearance, resulting in an average 52% and 39% reduction in lamotrigine AUC and Cmax, respectively. Serum lamotrigine concentrations gradually increased during the course of the week of inactive medication (e.g. "pill-free" week), with pre-dose concentrations at the end of the week of inactive medication being, on average, approximately two-fold higher than during co-therapy. (see Dosage & Administration, for dosing instructions for women taking hormonal contraceptives, and Hormonal Contraceptives under Precautions).
Effects of lamotrigine on hormonal contraceptive pharmacokinetics: In a study of 16 female volunteers, a steady state dose of 300mg lamotrigine had no effect on the pharmacokinetics of the ethinyloestradiol component of combined oral contraceptive pill. A modest increase in oral clearance of the levonorgestrel component was observed, resulting in an average 19% and 12% reduction in levonorgestrel AUC and Cmax, respectively. Measurement of serum FSH, LH, and oestradiol during the study indicated some loss of suppression of ovarian hormonal activity in some women, although measurement of serum progesterone indicated that there was no hormonal evidence of ovulation in any of the 16 subjects. The impact of the modest increase in the levonorgestrel clearance, and the change in the serum FSH and LH, on ovarian ovulatatory activity is unknown (see Precautions). The effects of doses of lamotrigine other than 300mg/day have not been studied and studies with other female hormonal preparations have not been conducted.
Interactions involving other medications: In a study in 10 male volunteers, rifampicin increased lamotrigine clearance and decrease lamotrigine half-life due to induction of the hepatic enzymes responsible for glucuronidation. In patients receiving concomitant therapy with rifampicin, the treatment regimen recommended for lamotrigine and concurrent glucuronidation inducers should be used (see Dosage & Administration).
In a study in healthy volunteers, lopinavir/ritonavir approximately halved the plasma concentrations of lamotrigine, probably by induction of glucuronidation. In patients receiving concomitant therapy with lopinavir/ritonavir, the treatment regimen recommended for lamotrigine and concurrent glucuronidation inducers should be used (see Dosage & Administration). Data from in vitro assessment of the effect of lamotrigine at OCT 2 demonstrate that lamotrigine, but not the N(2)-glucuronide metabolite, is an inhibitor of OCT 2 at potentially clinically relevant concentrations. These data demonstrate that lamotrigine is an inhibitor of OCT 2, with an IC 50 value of 53.8 μM (see Precautions).
Interactions involving laboratory tests: LAMOTRIX has been reported to interfere with the assay used in some rapid urine drug screens, which can result in false positive readings, particularly for phencyclidine (PCP). A more specific alternative chemical method should be used to confirm a positive result.
Caution For Usage
Incompatibilities:None reported.
Instruction for Use/Handling: None.
Storage
Store at temperature not exceeding 30°C, protected from moisture and light.
MIMS Class
ATC Classification
N03AX09 - lamotrigine ; Belongs to the class of other antiepileptics.
Presentation/Packing
Tab (beige, round, flat) 50 mg x 3 x 10's. 100 mg x 3 x 10's.
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