LAMICTAL
Clinical safety rating: caution
Comprehensive clinical and safety monograph for LAMICTAL (LAMICTAL).
Lamotrigine is a triazine antiepileptic drug that inhibits voltage-sensitive sodium channels, stabilizing neuronal membranes and modulating presynaptic transmitter release of excitatory amino acids like glutamate and aspartate.
| Metabolism | Primarily metabolized by glucuronidation via UGT1A4 to inactive N-glucuronide; minor role of UGT2B7; not significantly metabolized by CYP450 enzymes. |
| Excretion | Renal (70% as glucuronide metabolites, 2% as unchanged drug); fecal (2%); biliary (minor). |
| Half-life | 14 hours (monotherapy); 7 hours (with enzyme-inducers); 30 hours (with valproate). |
| Protein binding | 55% (albumin). |
| Volume of Distribution | 0.9-1.3 L/kg (indicating extensive tissue distribution). |
| Bioavailability | 98% (oral, immediate-release). |
| Onset of Action | Oral: 2-4 hours (seizure protection after initial titration); IV: not applicable. |
| Duration of Action | 12-24 hours (monotherapy, dose-dependent); clinical effect persists with steady state after 3-5 half-lives. |
| Molecular Weight | 256.09 |
| Action Class | Sodium channel modulators (AED) |
| Brand Substitutes | Lametec 200 OD Tablet, Ictasure 200mg Tablet SR, JI Lmt OD 200mg Tablet SR, Lamocent OD 200mg Tablet SR, Flylep 200mg Tablet SR, Flylep 100mg Tablet SR, Lamiwell 100 Tablet SR, Voltrigin 100mg Tablet SR, Ictasure 100mg Tablet SR, Lamokem OD 100 Tablet SR |
Initial: 25 mg orally once daily for 2 weeks, then 50 mg once daily for 2 weeks, then 100 mg once daily for 1 week, then 150 mg twice daily or 200 mg twice daily (if taking valproate, reduced regimen).
| Dosage form | TABLET |
| Renal impairment | No specific dose adjustment provided; use with caution if CrCl < 10 mL/min, as active metabolite may accumulate. |
| Liver impairment | Child-Pugh Class B: reduce dose by 50%; Child-Pugh Class C: reduce dose by 75%. |
| Pediatric use | For epilepsy (2-12 years): initial 0.15 mg/kg/day for 2 weeks, then 0.3 mg/kg/day for 2 weeks, then titrate by 0.3 mg/kg/day every 1-2 weeks; maintenance 1-5 mg/kg/day (max 200 mg/day). For bipolar disorder (10-17 years): similar adult regimen based on weight. |
| Geriatric use | Start at lower end of dosing range due to possible decreased renal/hepatic function; typical initial 25 mg/day with slower titration. |
| 1st trimester | Associated with increased risk of oral clefts (first trimester exposure). Risk of neural tube defects. Use only if benefit outweighs risk. |
| 2nd trimester | Limited data; crosses placenta. Consider monitoring for adverse effects. May require dose adjustments due to pregnancy physiology. |
| 3rd trimester | Risk of withdrawal in neonate. Use lowest effective dose. Supplement with folate. |
Clinical note
Comprehensive clinical and safety monograph for LAMICTAL (LAMICTAL).
| Placental transfer | Extensive placental transfer; cord blood levels similar to maternal plasma (ratio ~1.0). |
| Breastfeeding | Lamotrigine is excreted into breast milk in moderate amounts (milk-to-plasma ratio ~0.6). Infant serum levels can reach therapeutic levels; monitor for drowsiness, poor suckling. Generally considered compatible with breastfeeding, but weigh risks vs benefits. |
■ FDA Black Box Warning
Serious skin rashes (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis) requiring hospitalization and discontinuation; risk increased in pediatric patients, co-administration with valproate, or rapid dose titration.
| Serious Effects |
Hypersensitivity to lamotrigine or any component of the formulationHistory of lamotrigine-induced rash (including Stevens-Johnson syndrome)
| Precautions | Life-threatening skin rashes (SJS/TEN), hypersensitivity reactions including DRESS syndrome, hemophagocytic lymphohistiocytosis, cardiac rhythm abnormalities (PR prolongation, AV block), aseptic meningitis, blood dyscrasias, suicidal thoughts/behavior, exacerbation of seizures, withdrawal seizures, multi-organ hypersensitivity reactions. |
| Food/Dietary | No clinically significant food interactions. Lamotrigine may be taken with or without food. Grapefruit juice has no known interaction with lamotrigine. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Lamotrigine (LAMICTAL) is associated with an increased risk of major congenital malformations, particularly orofacial clefts (cleft lip/palate), when used during the first trimester. The absolute risk for cleft palate is approximately 0.2-0.3% versus 0.06% in the general population. Risk of neural tube defects is not significantly elevated. Third-trimester exposure may cause neonatal withdrawal or toxicity (e.g., tremor, hypotonia). Use during pregnancy is acceptable if benefits outweigh risks; monotherapy at lowest effective dose preferred. |
| Fetal Monitoring | Baseline and periodic monitoring of serum lamotrigine levels, especially during pregnancy and postpartum. Fetal ultrasound to screen for orofacial clefts (e.g., at 18-20 weeks gestation). Monitor mother for signs of toxicity (e.g., rash, dizziness, ataxia). Evaluate infant for withdrawal symptoms (e.g., jitteriness, hypotonia) after delivery. |
| Fertility Effects | Lamotrigine does not appear to significantly impair fertility in either men or women. No known effects on spermatogenesis or ovulation in animal studies. However, women with epilepsy may have altered menstrual cycles due to underlying condition or concurrent medications. |
| Clinical Pearls | Lamotrigine requires slow titration to minimize risk of Stevens-Johnson syndrome. Starting dose for epilepsy is 25 mg daily for 2 weeks, then 50 mg daily for 2 weeks, then increase by 50-100 mg every 1-2 weeks. For bipolar disorder, starting dose is 25 mg daily for 2 weeks, then 50 mg daily for 2 weeks, then 100 mg daily for 1 week, then target 200 mg daily. Concomitant valproate doubles lamotrigine half-life and requires halving the lamotrigine dose. Concomitant enzyme-inducing AEDs (e.g., carbamazepine, phenytoin) reduce lamotrigine half-life and require doubling the usual target dose. Discontinue lamotrigine if rash, fever, or lymphadenopathy occurs. Monitor for hypersensitivity reactions, especially in the first 2-8 weeks. |
| Patient Advice | Take lamotrigine exactly as prescribed; do not change dose without consulting your doctor. · Swallow tablets whole or chewable tablets may be chewed or crushed; oral disintegrating tablets dissolve on tongue. · If you miss a dose, take it as soon as you remember unless close to next dose; do not double up. · Report any new rash, fever, swollen lymph nodes, or mouth sores immediately; these may be signs of a serious allergic reaction. · Lamotrigine may cause dizziness, drowsiness, or blurred vision; avoid driving or operating machinery until you know how it affects you. · Do not stop taking lamotrigine suddenly, as withdrawal may trigger seizures or mood changes. · Use effective contraception if of childbearing potential; lamotrigine may reduce effectiveness of hormonal contraceptives. · Avoid alcohol, as it may worsen side effects like dizziness and drowsiness. |