Lamotrigine is an antiepileptic drug (AED) indicated for:
Epilepsy - adjunctive therapy in patients aged 2 years and older:
Epilepsy - monotherapy in patients aged 16 years and older.
Bipolar disorder - patients aged 18 years and older.
Lamotrigine is a phenyltriazine antiepileptic used to treat some types of epilepsy and bipolar disorder. Lamotrigine controls epileptic seizures by inhibiting voltage-sensitive sodium channels, thereby stabilizing neuronal membranes and consequently inhibiting presynaptic excitatory neurotransmitter (e.g., glutamate and aspartate) release.
The exact mechanism of action of lamotrigine is not fully elucidated, as it may exert cellular activities that contribute to its efficacy in a range of conditions. Although chemically unrelated, lamotrigine's actions resemble those of phenytoin and carbamazepine, inhibiting voltage-sensitive sodium channels, stabilizing neuronal membranes, thereby modulating the release of presynaptic excitatory neurotransmitters.
Lamotrigine likely acts by inhibiting sodium currents through selective binding to the inactive sodium channel, suppressing the release of the excitatory amino acid glutamate. The mechanism of action of lamotrigine in reducing anticonvulsant activity is likely the same in managing bipolar disorder. Studies on lamotrigine have identified its binding to sodium channels in a fashion similar to local anesthetics, which could explain the demonstrated clinical benefit of lamotrigine in some neuropathic pain states.
Lamotrigine displays binding properties to several different receptors. In laboratory binding assays, it demonstrates weak inhibitory effect on the serotonin 5-HT3 receptor. Lamotrigine also weakly binds to Adenosine A1/A2 receptors, α1/α2/β adrenergic receptors, dopamine D1/D2 receptors, GABA A/B receptors, histamine H1 receptors, κ-opioid receptor (KOR), mACh receptors, and serotonin 5-HT2 receptors with an IC50 > 100 µM. Weak inhibitory effects were observed at sigma opioid receptors. An in vivo study revealed evidence that lamotrigine inhibits Cav2.3 (R-type) calcium currents, which may also contribute to its anticonvulsant effects.
Epilepsy-
Table-1: Escalation Regimen for Lamotrigine in Patients Older than 12 Years with Epilepsy
Weeks 1 & 2:
Weeks 3 & 4:
Week 5 onward to maintenance:
Usual maintenance dose:
Table-2: Escalation Regimen for Lamotrigine in Patients Aged 2 to 12 Years with Epilepsy
Weeks 1 & 2:
Weeks 3 & 4:
In patients not taking Carbamazepine, Phenytoin, Phenobarbital, Primidone or Valproate: 0.6 mg/kg/day (in 2 divided doses)
Week 5 onward to maintenance:
Usual maintenance dose:
Table-3: The Initial Weight-Based Dosing Guide for Patients Aged 2 to 12 Years Taking Valproate (Weeks 1 to 4) with Epilepsy
Weeks 1 & 2:
Weeks 3 & 4:
Table-4: Escalation Regimen for Lamotrigine in Adults with Bipolar Disorder
Weeks 1 & 2:
Weeks 3 & 4:
Week 5:
Week 6:
Week 7:
Valproate increases lamotrigine concentrations more than 2-fold.Carbamazepine, phenytoin, phenobarbital, primidone, and rifampin decrease lamotrigine concentrations by approximately 40%.Estrogen-containing oral contraceptives decrease lamotrigine concentrations by approximately 50%. Protease inhibitors lopinavir/ritonavir and atazanavir/ritonavir decrease lamotrigine exposure by approximately 50% and 32% respectively.
Adult: Dizziness, headache, diplopia, ataxia, nausea, blurred vision, somnolence, pharyngitis, and rash.
Children: Vomiting, diarrhea, infection, fever, abdominal pain, and tremor.
Pregnancy Category C. Lamotrigine is excreted in human milk. Because of the potential for serious adverse reactions in nursing infants from Lamotrigine, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Discontinue at the first sign of rash. Blood dyscrasias (e.g., neutropenia, thrombocytopenia, pancytopenia): may occur. Monitor for signs of anemia, unexpected infection, or bleeding. Suicidal behavior and ideation: Monitor for suicidal thoughts or behaviors. Aseptic meningitis: Monitor for signs of meningitis.
Pediatric Use:
Epilepsy: Safety and effectiveness of Lamotrigine used as adjunctive treatment for partial-onset seizures were not demonstrated in very young pediatric patients aged 1 to 24 months.
Bipolar Disorder: Safety and effectiveness of Lamotrigine for the maintenance treatment of bipolar disorder were not established in pediatric patients aged 10 to 17 years.
Overdose has resulted in ataxia, nystagmus, seizures (including tonic-clonic seizures), decreased level of consciousness, coma, and intraventricular conduction delay.
Primary anti-epileptic drugs
Keep out of reach of children. Store in a dry place, below 25°C temperature, and protected from light.
What is Lamotrigine for?
What does Lamotrigine do?
What are the side effects of Lamotrigine?
What happens if you take too much Lamotrigine?
Can Lamotrigine be taken during pregnancy?
