Lamotrigine
Lamotrigine Lamictal
Lamotrigine
(lah- MAH-trih-jeen)
Pregnancy Category: C Lamictal Lamictal Chewable Dispersible Tablets (Rx)

Classification: Anticonvulsant

See Also: See also Anticonvulsants .

Action/Kinetics: Mechanism of anticonvulsant action not known. May act to inhibit voltage-sensitive sodium channels. This effect stabilizes neuronal membranes and modulates presynaptic transmitter release of excitatory amino acids such as glutamate and aspartate. Rapidly and completely absorbed after PO use. Peak plasma levels: 1.4-4.8 hr. t 1/2, after repeated doses: About 33 hr. Metabolized by the liver with metabolites and unchanged drug excreted mainly through the urine (94%). Lamotrigine induces its own metabolism. Eliminated more rapidly in clients who have been taking antiepileptic drugs that induce liver enzymes. However, valproic acid decreases the clearance of lamotrigine.

Uses: Adjunct in the treatment of partial seizures in adults with epilepsy. As an adjunct in treating of generalized seizures in adults and children with Lennox-Gastaut syndrome. Conversion to monotherapy in adults with partial seizures who are receiving a single enzyme-inducing anticonvulsant drug. Investigational: Adults with generalized tonic-clonic, absence, atypical absence, myoclonic seizures, and drug-resistant seizures in epilepsy syndromes with multiple seizures types.

Contraindications: Use during lactation and in children less than 16 years of age.

Special Concerns: Use with caution in clients with diseases or conditions that could affect metabolism or elimination of the drug, such as in impaired renal, hepatic, or cardiac function.
Serious rashes requiring hospitilzation have been noted, especially in children. Risk of rash may be increased by giving lamotrigine with valproic acid, exceeding the recommended initial dose, and exceeding the recommended dose escalation for lamotrigine. Most rashes occur within 2-8 weeks of starting treatment but some rashes are seen after chronic treatment (e.g., 6 months).

Side Effects: Side effects listed are those with an incidence of 0.1% or greater. CNS: Dizziness, ataxia, somnolence, headache, incoordination, insomnia, tremor, depression, anxiety, irritability, decreased memory, speech disorder, confusion, disturbed concentration, sleep disorder, emotional lability, vertigo, mind racing, amnesia, nervousness, abnormal thinking, abnormal dreams, agitation, akathisia, aphasia, CNS depression, depersonalization, dyskinesia, dysphoria, euphoria, faintness, hallucinations, hostility, hyperkinesia, hypesthesia, myoclonus, panic attack, paranoid reaction, personality disorder, psychosis, stupor. GI: N&V;, diarrhea, dyspepsia, constipation, tooth disorder, anorexia, dry mouth, abdominal pain, dysphagia, flatulence, gingivitis, gum hyperplasia, increased appetite, increased salivation, abnormal liver function tests, mouth ulceration, stomatitis, thirst. CV: Hot flashes, palpitations, flushing, migraine, syncope, tachycardia, vasodilation. Musculoskeletal: Arthralgia, joint disorder, myasthenia, dysarthria, muscle spasm, twitching. Hematologic: Anemia, ecchymosis, leukocytosis, leukopenia, lymphadenopathy, petechiae. Hypersensitivity: Fever, lymphadenopathy, rash, multiorgan dysfunction, disseminated intravascular coagulation. Respiratory: Rhinitis, pharyngitis, increased cough, dyspnea, epistaxis, hyperventilation. Dermatologic: Stevens-Johnson syndrome, toxic epidermal necrolysis pruritus, alopecia, acne, dry skin, eczema, erythema, hirsutism, maculopapular rash, sweating, urticaria. Ophthalmologic: Diplopia, blurred vision, nystagmus, abnormal vision, abnormal accommodation, conjunctivitis, oscillopsia, photophobia. GU: Dysmenorrhea, vaginitis, amenorrhea, female lactation, hematuria, polyuria, urinary frequency or incontinence, UTI, vaginal moniliasis. Body as a whole: Possibility of sudden unexplained death in epilepsy flu syndrome, fever, infection, neck pain, malaise, seizure exacerbation, chills, halitosis, facial edema, weight gain or loss, peripheral edema, hyperglycemia. Miscellaneous: Ear pain, tinnitus, taste perversion.

Overdose Management: Symptoms: Possibility of dizziness, headache, somnolence, coma. Treatment: Hospitalization with general supportive care. If indicated, induce emesis or perform gastric lavage. Protect the airway.

Drug Interactions: Acetaminophen / Serum lamotrigine levels Carbamazepine / 40% in lamotrigine levels Folate inhibitors / Lamotrigine inhibits dihydrofolate reductase Phenobarbital / 40% in lamotrigine levels Phenytoin / 45%-54% in lamotrigine levels Primidone / 40% in lamotrigine levels Valproic acid / Twofold in lamotrigine levels; 25% in valproic acid levels

How Supplied: Chewable Dispersible Tablet: 5 mg, 25 mg; Tablet: 25 mg, 100 mg, 150 mg, 200 mg

Dosage
?Tablets Treatment of partial seizures, lamotrigine added to valproic acid.
Adults and children over 12 years of age: Weeks 1 and 2, 25 mg q other day. Weeks 3 and 4, 25 mg/day. Maintenance: To achieve maintenance doses of lamotrigine of 100-200 mg/day, increase dose by 25-50 mg/day q 1-2 weeks. Children, 2-12 years: Weeks 1 and 2 0.15 mg/kg/day in 1 or 2 divided doses, rounded down to the nearest 5 mg. If the initial dose calculated is between 2.5 and 5 mg, give 5 mg on alternate days for the first 2 weeks. Weeks 3 and 4 0.3 mg/kg/day in 1 or 2 divided doses; round down to the nearest 5 mg. Maintenance: 1-5 mg/kg/day, not to exceed 200 mg/day in 1 or 2 divided doses. To reach maintenance dose, increase dose as follows q 1-2 weeks: Calculate 0.3 mg/kg/day and round this down to the nearest 5 mg; add this amount to the previously administered daily dose.
Partial seizures, lamotrigine added to enzyme-inducing antiepileptic drugs (e.g., carbamazepine, phenobarbital, phenytoin, primidone) without valproic acid.
Adults and children over 12 years: Weeks 1 and 2 50 mg/day. Weeks 3 and 4 100 mg/day in 2 divided doses. Maintenance: To achieve maintenance doses of 300-500 mg/day (in 2 divided doses), increase dose by 100 mg/day q 1-2 weeks. Children, 2-12 years: Weeks 1 and 2 0.6 mg/kg/day in 2 divided doses, rounded down to the nearest 5 mg. Weeks 3 and 4 1.2 mg/kg/day in 2 divided doses, rounded down to the nearest 5 mg. Maintenance: 5-10 mg/kg/day, to a maximum of 400 mg/day in 2 divided doses. To reach maintenance doses, increase the dose as follows q 1-2 weeks: Calculate 1.2 mg/kg/day and round down to the nearest 5 mg; add this amount to the previously administered daily dose.
Conversion from a single enzyme-inducing antiepileptic drug to lamotrigine alone.
Clients 16 years and older: 500 mg/day (maintenance dose) in 2 divided doses. To convert, titrate lamotrigine to 500 mg/day in 2 divided doses while maintaining the dose of the enzyme-inducing drug at a fixed level. Wtihdraw the enzyme-inducing drug by 20% decrements each q week over a 4-week period.