Lamotrigine

LAMICTAL

Open Lamotrigine in the interactive console ↗

Pronunciation: la-MOE-tri-jeen (la-MIK-tal)

Lamotrigine ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Lamotrigine ballicule

Lamotrigine LAMICTAL mascot mnemonic cartoon — Visual mnemonic: Lamotrigine mascot
**“Ictal Lamb”**
“ictal” refers to seizure

What it isVoltage-gated sodium-channel blocker with additional calcium and HCN effects; seizures and bipolar maintenance.

Why this oneMood stabilizer with the best evidence for preventing bipolar depression, and it is weight-neutral and non-sedating.

What limits itRash risk dictates slow titration; valproate raises exposure, while enzyme inducers and estrogen lower it. Restart cautiously after interruptions.

Pearls

Lowest malformation risk among mood stabilizers; preferred over valproate in pregnancy.
Too slow to titrate for acute bipolar depression.
Fewer cognitive effects than carbamazepine or topiramate.
Caution in structural or conduction heart disease: arrhythmia risk.

Lamotrigine molecular structure (skeletal formula) — Molecular structure: Lamotrigine

Lamotrigine prescription history

Animated chart of estimated U.S. prescriptions per year, Bipolar disorder meds (1954–2026). Lamotrigine enters in 1995 (estimated).

FDA-approved for

seizures (1994)
bipolar maintenance (2003)

Off-label

neuropathic pain

Classes and tags

Clinical profile

Therapeutic safety burden2 / 4

Overdose danger2 / 4

Weight-gain liability0 / 4

Sedation liability1 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk1 / 4

Legacy pregnancy categoryC

Defining liabilitySerious rash risk is concentrated during rapid titration or re-titration; dizziness and diplopia are common.

FDA label

Read the full label on DailyMed ↗

BOXED WARNING Serious skin rashes (Stevens-Johnson syndrome, toxic epidermal necrolysis), including rash-related death; risk higher in pediatric patients and with valproate coadministration or exceeding recommended dosing.

FDA dosing	Population	Start	Target	Max
Epilepsy — adjunctive therapy (partial-onset, PGTC, Lennox-Gastaut)	>12 yr; dosing depends on concomitant AED	Wk 1–2 25 mg QD, wk 3–4 50 mg/day (valproate: 25 mg QOD, then 25 mg QD; inducers no valproate: 50 mg/day, then 100 mg/day in 2 divided doses); wk 5+: +50 mg/day (valproate +25–50; inducers +100) every 1–2 wk	225–375 mg/day in 2 divided doses (valproate alone 100–200; valproate + inducers 100–400, in 1–2 doses; inducers no valproate 300–500 in 2 divided doses)	Undefined — no labeled max; benefit above Table 1 ranges not established (up to 700 mg/day used in inducer multidrug regimens without valproate; up to 200 mg/day with valproate alone)
Epilepsy — conversion to monotherapy (partial-onset)	≥16 yr	Per adjunctive escalation	500 mg/day divided BID	500 mg/day
Bipolar I disorder — maintenance	Adults	25 mg QD (25 mg QOD with valproate; 50 mg QD with inducers)	200 mg/day (100 with valproate; 400 with inducers)	200 mg/day
Epilepsy — adjunctive therapy (partial-onset, PGTC, Lennox-Gastaut)	2–12 yr; mg/kg by concomitant AED; whole tablets only, round down (2- and 5-mg tablets for oral suspension; smallest 2 mg)	Neither valproate nor inducer: 0.3 mg/kg/day (1–2 doses) wk 1–2, 0.6 mg/kg/day (2 divided doses) wk 3–4; valproate: 0.15 then 0.3 mg/kg/day in 1–2 doses (Table 3: 6.7–14 kg 2 mg QOD→2 mg QD; 14.1–27 kg 2→4 mg QD; 27.1–34 kg 4→8 mg QD; 34.1–40 kg 5→10 mg QD); inducers no valproate: 0.6 then 1.2 mg/kg/day in 2 divided doses. Wk 5+: every 1–2 wk add 0.6 (valproate 0.3; inducers 1.2) mg/kg/day rounded down	4.5–7.5 mg/kg/day in 2 divided doses (valproate: 1–5 mg/kg/day, 1–3 with valproate alone; inducers no valproate: 5–15 mg/kg/day); <30 kg may need up to 50% more	300 mg/day (valproate: 200 mg/day; inducers no valproate: 400 mg/day)

Titration Increase at 1–2 week intervals per escalation tables; do not exceed recommended initial dose/escalation (rash risk).

Renal Reduced maintenance doses may be effective in significant renal impairment; use with caution.

Hepatic No adjustment for mild; reduce initial/escalation/maintenance ~25% for moderate–severe without ascites and ~50% for severe with ascites.

Instructions

Do not exceed recommended initial dose and escalation to reduce rash risk
Discontinue at first sign of rash unless clearly not drug-related
Discontinue by tapering over ≥2 weeks (~50% per week)
Adjust dose when starting/stopping estrogen-containing contraceptives

Available strengths

tab 25, 100, 150, 200 mg
chew tab 2, 5 mg

Cautions

Serious skin rash
Multiorgan hypersensitivity (DRESS)/hemophagocytic lymphohistiocytosis
Cardiac rhythm/conduction abnormalities
Blood dyscrasias
Aseptic meningitis
Suicidal behavior/ideation

Adverse reactions

Dizziness
Headache
Diplopia
Ataxia
Nausea
Blurred vision
Somnolence
Rash
Rhinitis/pharyngitis

Pregnancy No consistent increased malformation risk detected; may decrease fetal folate; clearance increases in pregnancy.

Lactation Undefined.

Cost

Lamotrigine (LAMICTAL)

What pharmacies pay · NADAC 9/30/26

Strength		#/mo	generic $/mo	CostPlus
25 mg	tab	30 qd	$0.80	offered
100 mg	tab	30 qd	$1.46	offered
150 mg	tab	30 qd	$2.08	offered
200 mg	tab	30 qd	$2.48	offered
2 mg	chew tab	30 qd		not offered
5 mg	chew tab	30 qd	$5.02	offered