Lamotrigine

What it is and how it works

Mechanism of Action The precise mechanism(s) by which lamotrigine exerts its anticonvulsant action are unknown. In animal models designed to detect anticonvulsant activity, lamotrigine was effective in preventing seizure spread in the maximum electroshock (MES) and pentylenetetrazol (scMet) tests, and prevented seizures in the visually and electrically evoked after-discharge (EEAD) tests for antiepileptic activity. Lamotrigine also displayed inhibitory properties in the kindling model in rats both during kindling development and in the fully kindled state. The relevance of these models to human epilepsy, however, is not known.

Mechanism class: Organic Cation Transporter 2 Inhibitors · Dihydrofolate Reductase Inhibitors

Indications

Lamotrigine orally disintegrating tablets are indicated for: Epilepsy - adjunctive therapy in patients aged 2 years and older: • partial-onset seizures. • primary generalized tonic-clonic (PGTC) seizures. • generalized seizures of Lennox-Gastaut syndrome. Epilepsy - monotherapy in patients aged 16 years and older: Conversion to monotherapy in patients with partial-onset seizures who are receiving treatment with carbamazepine, phenytoin, phenobarbital, primidone, or valproate as the single antiepileptic drug. Bipolar disorder : Maintenance treatment of bipolar I disorder to delay the time to occurrence of mood episodes in patients treated for acute mood episodes with standard therapy. Limitations of Use: Treatment of acute manic or mixed episodes is not recommended. Effectiveness of lamotrigine orally disintegrating tablets in the acute treatment of mood episodes has not been established.

Dosage and administration (summary)

• Dosing is based on concomitant medications, indication, and patient age. ( 2.1 , 2.2 , 2.3 , 2.4 ) • To avoid an increased risk of rash, the recommended initial dose and subsequent dose escalations should not be exceeded. • Do not restart lamotrigine in patients who discontinued due to rash unless the potential benefits clearly outweigh the risks. ( 2.1 , 5.1 ) • Adjustments to maintenance doses will be necessary in most patients starting or stopping estrogen-containing oral contraceptives. ( 2.1 , 5.9 ) • Discontinuation: Taper over a period of at least 2 weeks (approximately 50% dose reduction per week).

Contraindications

Lamotrigine is contraindicated in patients who have demonstrated hypersensitivity (e.g., rash, angioedema, acute urticaria, extensive pruritus, mucosal ulceration) to the drug or its ingredients . Hypersensitivity to the drug or its ingredients. (Boxed Warning, 4 )

Warnings and precautions

• Life-threatening serious rash and/or rash-related death: Discontinue at the first sign of rash, unless the rash is clearly not drug related. (Boxed Warning, 5.1 ) • Hemophagocytic lymphohistiocytosis: Consider this diagnosis and evaluate patients immediately if they develop signs or symptoms of systemic inflammation. Discontinue lamotrigine if an alternative etiology is not established. • Fatal or life-threatening hypersensitivity reaction: Multiorgan hypersensitivity reactions, also known as drug reaction with eosinophilia and systemic symptoms, may be fatal or life threatening.

Pregnancy

Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AEDs, including lamotrigine, during pregnancy. Encourage women who are taking lamotrigine during pregnancy to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry by calling 1-888-233-2334 or visiti…

Storage and supply

Lamotrigine Orally Disintegrating Tablets, USP 25 mg, white to off white colored, may be speckled, round shaped, flat-faced, beveled edge tablets debossed with “1O” on one side and plain on other side.

Source: Lamotrigine (Lamotrigine) — US FDA prescribing information, 2026-03-26, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.