lamotrigine

Brand: Lamictal, Lamictal XR

⚠ BBW Prototype: phenytoin

Drug Class: antiepileptic / mood stabilizer

Drug Family: antiepileptic

Subclass: phenyltriazine

Organ Systems: cns

Mechanism of Action

Stabilizes neuronal membranes by blocking voltage-sensitive sodium channels and inhibiting glutamate release; also modulates voltage-gated calcium channels.

voltage-gated sodium channelsvoltage-gated calcium channels

Indications

focal-onset seizures
primary generalized tonic-clonic seizures
Lennox-Gastaut syndrome
bipolar disorder (maintenance)
bipolar depression

Contraindications

hypersensitivity to lamotrigine

Adverse Effects

Common

dizziness
headache
diplopia
ataxia
nausea
rash (benign maculopapular)

Serious

Stevens-Johnson syndrome
toxic epidermal necrolysis
DRESS syndrome
aseptic meningitis
hemophagocytic lymphohistiocytosis

Pharmacokinetics (ADME)

Absorption	~98% oral bioavailability
Distribution	Protein binding 55%; Vd 0.9–1.3 L/kg
Metabolism	Hepatic glucuronidation (UGT1A4); significant drug interactions via glucuronidation induction/inhibition
Excretion	Renal as glucuronide conjugates; ~10% unchanged
Half-life	25–33 hours (monotherapy); 13–15 hours with enzyme inducers; 42–72 hours with valproate
Onset	Days to weeks
Peak	1.4–4.8 hours
Duration	24 hours
Protein Binding	55%
Vd	0.9–1.3 L/kg

Drug Interactions

Drug / Agent	Mechanism	Severity
valproate	inhibits UGT1A4, doubles lamotrigine half-life — must halve lamotrigine dose	major
carbamazepine	CYP induction reduces lamotrigine levels by ~50%	major
oral contraceptives (estrogen)	estrogen induces UGT1A4, reducing lamotrigine levels by ~50%	major

Nursing Considerations

Titrate very slowly — do not exceed recommended titration schedule; rapid titration dramatically increases Stevens-Johnson syndrome risk
Instruct patient to report any rash immediately and discontinue lamotrigine pending evaluation — even a 'benign' rash requires clinical assessment
When adding to valproate, start at 25 mg every other day (vs 25 mg daily in monotherapy) due to markedly reduced clearance
Monitor for mood symptoms; lamotrigine is FDA-approved for bipolar maintenance but is less effective for acute mania than for depression

Clinical Pearls

Lamotrigine is the preferred AED for women of childbearing age due to relatively low teratogenic risk, but estrogen-containing contraceptives reduce its levels by 50%
Unlike most AEDs, lamotrigine is effective for bipolar depression — a common unmet need given that most mood stabilizers target mania preferentially

Safety Profile

Pregnancy safe

Lactation use-with-caution

Renal Adjustment Required

Hepatic Adjustment Required

TDM Not required

Concordance Terms

Cross-referenced clinical concepts — click any term to see all content where it appears.

Antiepileptic / Mood Stabilizer Bipolar Depression Bipolar Disorder (maintenance) Focal-onset Seizures Lennox-Gastaut Syndrome Primary Generalized Tonic-clonic Seizures

← Back to Medications