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. |
| 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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for LAMICTAL (LAMICTAL).
| Breastfeeding | Lamotrigine is excreted in breast milk with a milk-to-plasma (M/P) ratio of approximately 0.4 to 0.6. Infant serum concentrations can reach therapeutic levels (up to 30% of maternal). Cases of infant apnea, rash, and drowsiness have been reported, but risk is generally low. Benefit of breastfeeding likely outweighs risk, but monitor infant for sedation, poor feeding, or rash. |
| 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. |
■ 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 formulation.
| 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. |
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| 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. |