lamotrigine: clinical use

Prescribing considerations

• Verify indication: the bipolar licence is prevention of depressive episodes in adults with bipolar I disorder, not acute mood episodes.
• Assess any previous lamotrigine-associated rash or hypersensitivity and review interacting medicines before initiation or reintroduction.
• Serious-rash risk is associated with excessive initial exposure or escalation and concomitant valproate.
• Use caution in renal failure and adjust treatment for clinically significant hepatic impairment according to the product SmPC.
• Carefully consider use in Brugada syndrome, cardiac channelopathy, structural heart disease, heart block or ventricular arrhythmia; cardiology input may be appropriate.
• For epilepsy, decide with the patient or carer whether continuity of a particular manufacturer's product is clinically important.

Contraindications and cautions

• Hypersensitivity to lamotrigine or a formulation excipient.
• Do not reintroduce lamotrigine after lamotrigine-associated Stevens–Johnson syndrome, toxic epidermal necrolysis or DRESS.
• Do not reintroduce it after lamotrigine-associated aseptic meningitis.

Monitoring

• Promptly assess any rash, fever, lymphadenopathy, facial swelling or other systemic hypersensitivity feature.
• Monitor seizure control, mood symptoms and suicidal thoughts or behaviour.
• Consider lamotrigine concentrations when pregnancy or oestrogen-containing treatment changes are expected to alter exposure.
• Assess for neurological toxicity or reduced efficacy when interacting medicines are started or stopped.
• Investigate blood counts, liver function, renal function and inflammatory markers when clinical features suggest systemic hypersensitivity, organ toxicity or haemophagocytic lymphohistiocytosis.

Clinical pharmacology

Lamotrigine blocks voltage-gated sodium channels and reduces glutamate release. It undergoes mainly UGT-mediated glucuronidation; clearance is strongly affected by enzyme inducers, valproate, pregnancy and oestrogens.

Formulation and product differences

• Selected products include conventional tablets, chewable/dispersible tablets and an oral suspension.
• Conventional tablets are swallowed whole; chewable/dispersible tablets offer three administration options.
• The oral suspension must be shaken before measurement and must not be mixed with other medicines or administered through feeding tubes.
• Excipients differ between products; check the product-specific SmPC when allergy, intolerance or enteral administration is relevant.

Dispersible tablet

Route: Oral

Strengths: 25 mg, 100 mg

Oral suspension

Route: Oral

Strengths: 10 mg/mL

Tablet

Route: Oral

Strengths: 25 mg, 50 mg, 100 mg, 200 mg