Lamotrigine

A to Z Drug Facts

Lamotrigine

 Action
 Indications
 Contraindications
 Route/Dosage
 Interactions
 Lab Test Interferences
 Adverse Reactions
 Precautions
Patient Care Considerations
 Administration/Storage
 Assessment/Interventions
 Patient/Family Education


lah-MOE-trih-JEEN
Lamictal
Tablets: 25 mg, Tablets: 100 mg, Tablets: 150 mg, Tablets: 200 mg, Tablets, chewable dispersible: 2 mg, Tablets, chewable dispersible: 5 mg, Tablets, chewable dispersible: 25 mg
Class: Anticonvulsant

 Action Chemically unrelated to existing antiepileptic drugs (AEDs); precise mechanism(s) unknown. One proposed mechanism suggests inhibition of voltage-sensitive sodium channels, thereby stabilizing neuronal membranes which modulates presynaptic transmitter release of excitatory amino acids (eg, glutamate, aspartate).

 Indications

Epilepsy: Adjunctive therapy in the treatment of partial seizures in adults and as adjunctive therapy in the generalized seizures of Lennox-Gastaut syndrome in pediatric and adult patients. Conversion to monotherapy in adults with partial seizures who are receiving treatment with a single enzyme-inducing AED (EIAED).

May be useful in adults with generalized tonic-clonic, absence, atypical absence, and myoclonic seizures.

 Contraindications Standard considerations.

 Route/Dosage As add-on therapy

Lamotrigine Plus AED Regimen Containing Valproic Acid:

CHILDREN (2 to 12 yr): PO Wk 1 and 2: 0.15 mg/kg/day in 1 to 2 divided doses. Wk 3 and 4: 0.3 mg/kg/day in 1 to 2 divided doses. Maintenance dose: 1 to 5 mg/kg/day (max 200 mg/day in 1 to 2 divided doses).

ADULTS (> 12 yr): PO Wk 1 and 2: 25 mg every other day. Wk 3 and 4: 25 mg once a day. Maintenance dose: 100 to 400 mg/day in 1 to 2 divided doses. To achieve, escalate dose by 25 to 50 mg/day q 1 to 2 wk.

Lamotrigine Plus EIAEDs without Valproic Acid:

CHILDREN (2 to 12 yr): PO Wk 1 and 2: 0.6 mg/kg/day in 2 divided doses. Wk 3 and 4: 1.2 mg/kg/day in 2 divided doses. Maintenance dose: 5 to 15 mg/kg/day (max 400 mg/day in 2 divided doses).

ADULTS (> 12 yr): PO Wk 1 and 2: 50 mg/day. Wk 3 and 4: 100 mg/day in 2 divided doses. Maintenance dose: 300 to 500 mg/day in 2 divided doses. To achieve, escalate dose by 100 mg/day q wk.

Patients receiving multi-drug regimens employing EIAEDs without valproic acid can have a maintenance dose of lamotrigine as high as 700 mg/day. With valproic acid, maintenance doses as high as 200 mg/day have been used. Patients receiving valproic acid and lamotrigine as a 2-drug regimen only cannot be given a safe and effective dose.

 Interactions

Acetaminophen, Carbamazepine, Primidone, Phenobarbital, Phenytoin, and Valproic Acid: May affect lamotrigine concentration.

Carbamazepine, Folate Inhibitors, and Valproic Acid: May be affected by lamotrigine.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Dizziness; ataxia; somnolence; tremor; depression; anxiety; headache; insomnia; convulsions; irritability; incoordination. DERMATOLOGIC: Rash (can be life threatening); pruritis; sweating. GI: Nausea; vomiting; diarrhea; dyspepsia; constipation; abdominal pain; anorexia. GU: Dysmenorrhea; vaginitis; amenorrhea; urinary tract infection. RESPIRATORY: Rhinitis; pharyngitis; bronchitis; pneumonia. OTHER: Flu syndrome; fever; neck pain; diplopia; blurred vision.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Children: Safety and efficacy in children < 16 yr not established for uses other than the above listing. Melanin-Containing Tissues: Lamotrigine binds to melanin and may cause toxicity with possibility of long-term ophthalmologic effects. Special Risk Patients: Use with caution in renal/hepatic/cardiac function impairment. Photosensitivity: Photoallergy or phototoxicity may occur. Withdrawal Seizures: AEDs should not be abruptly discontinued because of possibility of increasing seizure frequency. Taper dose over a 2-week period. Rash: Serious rash such as Stevens-Johnson syndrome may occur; contact health care provider immediately. Renal Function Impairment: If significant impairment, reduce maintenance doses. Discontinuation Strategy: Administer a stepwise reduction of dose (50%/wk) over a 2-wk period. Discontinuing an EIAED may prolong the half-life of lamotrigine; discontinuing valproic acid may shorten the half-life of lamotrigine.


PATIENT CARE CONSIDERATIONS


 Administration/Storage

 Assessment/Interventions

 Patient/Family Education

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Copyright
© 2003 Facts and Comparisons
David S. Tatro
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