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Lamotrigine information from DrugsUpdate  

See Available Brands of Lamotrigine in India

P - Caution when used during pregnancy
L - Caution when used during lactation

Lamotrigine by GlaxoSmithKline is an anticonvulsant drug used in the treatment of epilepsy and bipolar disorder. For epilepsy it is used to treat partial seizures, primary and secondary tonic-clonic seizures, and seizures associated with Lennox-Gastaut syndrome. Lamotrigine also acts as a mood stabilizer. It is approved for the maintenance treatment of bipolar type I. Chemically unrelated to other anticonvulsants (due to Lamotrigine being a Phenyltriazine), lamotrigine has relatively few side-effects and does not require blood monitoring in monotherapy. The exact way lamotrigine works is unknown. Some think that it is a Na+ (sodium) channel blocker, though it is interesting to note that lamotrigine shares very few side-effects with other, unrelated anticonvulsants known to inhibit sodium channels, (e.g. Oxcarbazepine), which may suggest that lamotrigine has a different mechanism of action. The drug information provided at the time of prescription notes that "it is thought to work by restoring the balance of certain natural substances (neurotransmitters) in the brain." Lamotrigine is inactivated by hepatic glucuronidation.

Pharmacodynamics

Pharmacokinetics

Lamotrigine inhibits voltage-sensitive sodium channels, thereby stabilising neuronal membranes and consequently inhibiting pathological release of excitatory amino acids (e.g. glutamate and aspartate). These amino acids play a role in the generation and spread of epileptic seizures.

Absorption

Well absorbed from the GI tract (oral); peak plasma concentrations after 2.5 hours.

Distribution

Widely distributed; enters breast milk.

Metabolism

Extensively hepatic.

Excretion

Via urine (as glucuronide conjugate); 24 hours (elimination half-life at steady state).

Lamotrigine Indications / Lamotrigine Uses

Information Not Available

Lamotrigine Adverse Reactions / Lamotrigine Side Effects

Skin eruptions usually maculopapular in nature, nausea, headache, tiredness, dizziness, ataxia, irritability/aggression, tremor, agitation, confusion, hallucination, diplopia, blurred vision. Haematological abnormalities e.g. leucopenia and thrombocytopenia. Elevations of LFTs. Arthralgia, pain and back pain.

Potentially Fatal: Stevens-Johnson syndrome and toxic epidermal necrolysis.

Precautions

Warnings
Serious rashes requiring hospitalization (including Stevens-Johnson syndrome) have been reported in 0.8% of children receiving lamotrigine as adjunctive therapy for epilepsy, 0.3% of adults receiving lamotrigine as adjunctive therapy for epilepsy, 0.08% of adults receiving lamotrigine as initial monotherapy for bipolar and other mood disorders, and 0.13% of adults receiving lamotrigine as adjunctive therapy for bipolar and other mood disorders. Other than age (children are at greatest risk), there are no other identified risk factors. There are suggestions that the risk of rash may be increased by: coadministration of lamotrigine with valproate, exceeding recommended initial dose of lamotrigine, or exceeding recommended dose escalation for lamotrigine. Almost all fatal cases have occurred within the first 2 to 8 wk of therapy, but isolated cases have been reported after prolonged (eg, 6 months) use. Discontinue lamotrigine at the first sign of rash, unless the rash is clearly not drug related.

Monitor

Because of possible pharmacokinetic interactions between lamotrigine and other AEDs, monitoring of plasma levels may be indicated, particularly during dosage adjustments.

Overdosage
Symptoms: Nystagmus and muscle hypertonicity, QRS interval prolongation, low-grade fever, erythema, and periorbital oedema, generalised tonic-clonic seizures, tremor, muscle weakness, ataxia, hypertonia. Management: Gastric lavage and activated charcoal.

Special Precautions

Hepatic or renal impairment. Closely monitor patient. Monitor children's body wt. Advise patient to report any hypersensitivity reaction. Avoid abrupt withdrawal unless severe skin reactions have developed. May impair ability to drive or operate machinery. Pregnancy and lactation.

Other Drug Interactions

Metabolism enhanced by enzyme-inducing drugs e.g. phenytoin, carbamazepine, phenobarbitone, primidone, rifampicin, ethinyloestradiol/levonorgestrel combination. Metabolism reduced by sodium valproate.

Other Interactions

Information Not Available

Dosage

Oral
Epilepsy
Adult: Initially, 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter, increase the dose by a max of 50-100 mg every 1-2 weeks to usual maintenance doses of 100-200 mg daily, as a single dose or in 2 divided doses. Some patients may require up to 500 mg daily.
Child: >12 years: Initially, 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter, increase the dose by a max of 50-100 mg every 1-2 weeks to usual maintenance doses of 100 -200 mg daily, as a single dose or in 2 divided doses. Some patients may require up to 500 mg daily. <12 years: Not recommended.
Max Dosage: Adult: 500 mg daily.

Hepatic impairment: Moderate impairment (Child-Pugh category B): Reduce dose by about 50%. Severe impairment (Child-Pugh category C): Reduce dose by about 75%.

Oral

Adjunct in epilepsy
Adult: With valproate: Initially, 25 mg on alternate days for 2 weeks followed by 25 mg once daily for 2 weeks; thereafter, increase by a max of 25-50 mg every 1-2 weeks; usual maintenance doses: 100-200 mg daily in 1-2 divided doses. With enzyme-inducing antiepileptics but not with valproate: 50 mg once daily for 2 weeks followed by 50 mg bid for 2 weeks; thereafter, increase by a max of 100 mg every 1-2 weeks; usual maintenance doses: 200-400 mg/day in 2 divided doses; up to 700 mg/day in some patients. With oxcarbazepine but no enzyme-inducing or -inhibiting antiepileptics: 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter increase dose by a max of 50-100 mg every 1-2 weeks; usual maintenance doses: 100-200 mg daily in 1-2 divided doses; up to 500 mg daily in some patients.
Child: With valproate: Initially, 0.15 mg/kg once daily for 2 weeks followed by 0.3 mg/kg once daily for 2 weeks; thereafter, increase by a max of 0.3 mg/kg every 1-2 weeks to usual maintenance doses of 1-5 mg/kg once daily or in 2 divided doses.

Hepatic impairment: Moderate impairment (Child-Pugh category B): Reduce dose by about 50%. Severe impairment (Child-Pugh category C): Reduce dose by about 75%.

Oral
Bipolar disorder
Adult: Monotherapy: Initially, 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter, double the daily dose at weekly intervals to usual maintenance dose of 200 mg daily. Max dose: 200 mg/day. With valproate: Initially, 25 mg every other day for 2 weeks followed by 25 mg once daily for 2 weeks; thereafter, double the daily dose at weekly intervals to usual maintenance dose of 100 mg daily. With enzyme-inducing antiepileptics but not with valproate: Initially, 50 mg once daily for 2 weeks followed by 100 mg daily in 2 divided doses for 2 weeks; thereafter, increase in 100-mg increments weekly to usual maintenance dose of 400 mg daily in 2 divided doses.

Hepatic impairment: Moderate impairment (Child-Pugh category B): Reduce dose by about 50%. Severe impairment (Child-Pugh category C): Reduce dose by about 75%.

Food(before/after)

May be taken with or without food

List of Contraindications

Lamotrigine and Pregnancy

Caution when used during pregnancy

Category C: Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Lamotrigine and Lactation

Caution when used during lactation

Lamotrigine and Children

For the treatment of partial seizures and for generalized seizures of Lennox-Gastaut syndrome, safety and efficacy not established for children younger than 2 years of age. Safety and efficacy not established in patients younger than 18 years of age with bipolar disorder.

Lamotrigine and Geriatic

Cautiously select dosage, usually starting at the lower end of the dosing range, reflecting the greater frequency of decreased hepatic and renal function, and comorbidity.

Lamotrigine and Other Contraindications

Information Not Available

Storage

Oral
Store below 30°C (86°F)

Lab interference

Oral
Store below 30°C (86°F)

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