DailyMed-verified antiseizure indications

Indication / use

Label / evidence summary: Lamictal immediate-release: adjunctive treatment of focal-onset, primary generalized tonic-clonic seizures, and generalized Lennox-Gastaut syndrome seizures from age 2 years; specified conversion to monotherapy for focal seizures from age 16 years. Lamictal XR: adjunctive treatment of focal-onset or primary generalized tonic-clonic seizures and specified focal-seizure conversion to monotherapy from age 13 years. Neither is labeled for initial monotherapy.
Role: Maintenance
Class: Sodium-channel inhibition with reduced excitatory transmitter release

Indications checked 26 September 2026. Product, route, age, and treatment-role limits apply. A DailyMed listing alone does not establish FDA approval.

Lamictal IR/ODT/dispersible U.S. label
Focal seizures, Generalized tonic-clonic seizures, Lennox-Gastaut syndrome · 2 years and older · Maintenance
Adjunctive; IR conversion to monotherapy is labeled from age 16 under specified regimens.
- Representative source · Lamictal IR/ODT/dispersible — DailyMed label (PDF) ↗
- Representative source · DailyMed label page ↗
Lamictal XR U.S. label
Focal seizures, Generalized tonic-clonic seizures · 13 years and older · Maintenance
Adjunctive; focal conversion to monotherapy has separate instructions.
- Representative source · Lamictal XR — DailyMed label (PDF) ↗
- Representative source · DailyMed label page ↗

Formulations & strengths

U.S. products unless another country is named. Strengths are per unit or stated volume.

Immediate-release tablet

Strengths: 25, 100, 150, 200 mg
Product note: Use the titration appropriate to interacting drugs.

Representative source · Lamictal · Immediate-release tablet — DailyMed label (PDF) ↗

Brand & formulation labels

Each link names the product and formulation it covers. Archived labels do not establish current availability.

Dosing & administration

Adult / product-specific schedule: Use the IR >12-year or XR ≥13-year table below, selected by co-medications. These are adjunctive epilepsy schedules; conversion to monotherapy has separate product-specific instructions.
Pediatric: IR ages 2–12: use the weight-based table below. Round down to achievable whole 2- or 5-mg tablets for oral suspension; use label Table 3 for low-weight children on valproate. XR is not established below age 13.
Titration / repeat dosing: Do not exceed the formulation/co-medication-specific initial dose or escalation. After interruption >5 half-lives, restart initial titration; half-life depends strongly on co-medications. After rash, do not restart unless the benefit clearly outweighs risk.

LAMICTAL IR, adjunctive epilepsy, age >12 years

Phase	With valproate	Neither valproate nor listed inducers	Inducer, without valproate
Weeks 1–2	25 mg every other day	25 mg/day	50 mg/day
Weeks 3–4	25 mg/day	50 mg/day	100 mg/day in 2 doses
Week 5 onward	Add 25–50 mg/day every 1–2 weeks	Add 50 mg/day every 1–2 weeks	Add 100 mg/day every 1–2 weeks
Usual maintenance	100–200 mg/day with valproate alone; 100–400 with valproate + inducer (1–2 doses)	225–375 mg/day in 2 doses	300–500 mg/day in 2 doses

Inducers here: carbamazepine, phenytoin, phenobarbital or primidone. Other inducers and monotherapy conversion require the full label.

LAMICTAL IR, adjunctive epilepsy, ages 2–12 years

Phase	With valproate	Neither valproate nor listed inducers	Inducer, without valproate
Weeks 1–2	0.15 mg/kg/day (1–2 doses)	0.3 mg/kg/day (1–2 doses)	0.6 mg/kg/day (2 doses)
Weeks 3–4	0.3 mg/kg/day (1–2 doses)	0.6 mg/kg/day (2 doses)	1.2 mg/kg/day (2 doses)
Week 5 onward	Add 0.3 mg/kg/day every 1–2 weeks	Add 0.6 mg/kg/day every 1–2 weeks	Add 1.2 mg/kg/day every 1–2 weeks
Usual maintenance	1–5 mg/kg/day, max 200 mg/day; valproate alone usually 1–3 mg/kg/day	4.5–7.5 mg/kg/day, max 300 mg/day	5–15 mg/kg/day, max 400 mg/day

Use whole-tablet rounding and the label’s low-weight valproate guide. Patients <30 kg may need up to 50% higher maintenance based on response; this is not an instruction to exceed label ceilings without specialist review.

LAMICTAL XR, adjunctive epilepsy, age ≥13 years (once daily)

Phase	With valproate	Neither	Inducer without valproate
Weeks 1–2	25 mg every other day	25 mg/day	50 mg/day
Weeks 3–4	25 mg/day	50 mg/day	100 mg/day
Week 5	50 mg/day	100 mg/day	200 mg/day
Week 6	100 mg/day	150 mg/day	300 mg/day
Week 7	150 mg/day	200 mg/day	400 mg/day
Week 8 onward	200–250 mg/day	300–400 mg/day	400–600 mg/day

Week 8+ increases must not exceed 100 mg/day at weekly intervals. XR monotherapy conversion is separate; IR-to-XR starts at the same total daily dose with monitoring.

Representative source · DOSAGE AND ADMINISTRATION ↗

Dose adjustment & concentrations

Renal impairment: Use caution; reduced maintenance may be effective in significant impairment.
Hepatic impairment: Reduce initial, escalation, and maintenance doses in moderate/severe impairment.
Serum reference information: Mayo reference interval 3–15 mcg/mL; collect before the next dose. The product label does not establish a universal therapeutic target. Compare with the individual effective baseline, especially in pregnancy or after interacting medicines change.

Laboratory reference interval and specimen guidance — checked 15 September 2026 ↗

Safety

Boxed warning: Boxed warning: serious rash, including Stevens–Johnson syndrome and toxic epidermal necrolysis. Pediatric patients, valproate co-use, excessive initial doses and rapid escalation increase risk. Stop at the first sign of rash unless clearly unrelated.
Contraindications: Hypersensitivity to lamotrigine or ingredients.
Serious precautions & monitoring: Stop at first rash unless clearly unrelated. Serious rash, DRESS, HLH, blood dyscrasias and aseptic meningitis. In clinically important structural/functional cardiac disease or conduction disorders, evaluate arrhythmia risk; other sodium-channel blockers may add risk.

Representative source · WARNINGS AND PRECAUTIONS ↗

Common / selected adverse effects

Dizziness
Headache
Diplopia
Ataxia
Nausea
Rash

Representative source · ADVERSE REACTIONS ↗

Drug interactions: toxicity & clinical action

Partner / combination	Clinical effect	Clinical action
Valproate	Inhibits glucuronidation and more than doubles lamotrigine concentration; serious rash risk rises, especially with a high starting dose or rapid escalation.	Use the valproate-specific low/slow titration. Reassess the lamotrigine dose whenever valproate is added or withdrawn; promptly assess rash.
Carbamazepine, phenytoin, phenobarbital, primidone or other glucuronidation inducers	Lower lamotrigine concentration; withdrawal can increase levels and toxicity.	Use the appropriate co-medication regimen and monitor dizziness, diplopia and ataxia after changes.
Estrogen-containing contraceptives	Can reduce lamotrigine concentration by about half; stopping estrogen or the pill-free interval can raise it.	Plan maintenance adjustments and symptom/level monitoring; do not make isolated pill-free-week adjustments.
Sulthiame / additional sodium-channel-active drugs	Sulthiame-associated lamotrigine level rises reported; additive neurologic/cardiac effects with sodium-channel blockers in susceptible patients.	Monitor levels/toxicity as indicated and review cardiac risk before combining.

Pregnancy & contraception

Fetal / neonatal risk: Registry and epidemiologic data have not shown an increased overall major-malformation frequency or consistent defect pattern with lamotrigine. AAN/AES/SMFM recommends considering it when appropriate for the epilepsy syndrome and seizure-control needs.
Contraception: Estrogen-containing contraception lowers lamotrigine exposure; levels can rise during pill-free intervals or after stopping. Coordinate initiation, withdrawal and dose changes. Report breakthrough bleeding; reduced contraceptive effectiveness cannot be excluded.
Pregnancy / postpartum monitoring: Lamotrigine concentrations may fall in pregnancy and rebound after delivery. Monitor clinical response and individualized concentrations; reassess the dose postpartum to limit toxicity.

Clinical evidence

Research summaries describe studied populations and outcomes; they do not add indications or constitute treatment recommendations.

Direct pivotal trial Guideline-supported off-label use

Trial summary

Study design / duration: Randomized, double-blind, placebo-controlled adjunctive focal-seizure and Lennox-Gastaut syndrome trials, generally using 8–16-week maintenance phases after baseline and titration; endpoints were seizure-frequency change and responder rate.
Primary endpoint: No single pivotal endpoint is identified in the cited source.
Results: Adjunctive focal-seizure trials showed median seizure-frequency reductions of approximately 20–36% with lamotrigine versus about 8% with placebo; results varied by trial and concomitant therapy. Lennox-Gastaut syndrome trial: major motor seizures fell 32% versus 9% with placebo.

Representative source · CLINICAL STUDIES ↗

Trial publications

Comparative evidence

Findings: SANAD II: open-label randomized initial treatment of newly diagnosed focal epilepsy, age ≥5. For time to 12-month remission, levetiracetam did not meet noninferiority versus lamotrigine; zonisamide did in the intention-to-treat analysis. Childhood absence randomized double-blind trial: freedom from treatment failure at 16–20 weeks was 53% ethosuximide, 58% valproate and 29% lamotrigine; this composite is not a seizure-freedom rate.

Mechanism of action

In vitro, inhibits voltage-sensitive sodium channels and limits repetitive firing, with downstream reduction of presynaptic excitatory amino-acid release, including glutamate and aspartate.
Reduced glutamate release is not direct AMPA or NMDA receptor antagonism. The relevance of this proposed mechanism to human seizure control is not fully established.

Representative source · Lamictal label: sodium channels and transmitter release ↗

Pharmacology

Adult values unless specified. Vd/F denotes apparent oral distribution volume.

Pharmacokinetics

Bioavailability: Approximately 98% absolute oral bioavailability for immediate-release lamotrigine.
Elimination half-life: Without interacting drugs: mean 32.8 hours after a single dose and 25.4 hours after repeated doses. With valproate: mean 70.3 hours after repeated doses; with enzyme-inducing ASMs: approximately 12.6 hours after repeated doses.
Volume of distribution: Apparent oral Vd/F approximately 0.9–1.3 L/kg.
Active metabolite(s): None clinically established: the predominant 2-N-glucuronide is inactive.
Active-metabolite half-life: Not applicable — no clinically established active metabolite.
Protein binding: ~55%
Metabolism / elimination: Hepatic glucuronidation (primarily UGT1A4)

The long half-life with valproate and short half-life with inducers are central to safe titration and restart decisions.

Representative source · U.S. product label — clinical pharmacology ↗

Molecular structure

Principal compound; salt and product forms may differ.
NIH PubChem structure and record ↗

Product history

Initial U.S. approval: 1994
Brands: Lamictal · Lamictal XR
Manufacturer / marketer: GSK (Lamictal/Lamictal XR)
Generic availability: Yes
Related drugs: Structurally distinct from other ASMs; functionally related to sodium-channel blockers.

Sources & review status

Representative sources are selected product labels, not an exhaustive list of generic manufacturers. Consult the exact product and formulation prescribed. Brand-name package inserts are linked separately.

Brand references: Lamictal / Lamictal ODT ↗ · Lamictal XR ↗

Indications and DailyMed PDFs checked: 2026-09-26. Other profile sources reviewed: 2026-09-15 · label revision noted at that review: 10/2025. This is a draft reference; final review is pending.

Lamotrigine