What are the side effects of lamotrigine?

Side Effects of Lamotrigine

Lamotrigine's most serious side effect is skin rash, which occurs in about 5% of patients and can rarely progress to severe reactions like Stevens-Johnson syndrome (0.4% of cases), while common mild side effects include headache, nausea, dizziness, and somnolence. 1, 2

Common Side Effects

Lamotrigine is generally well-tolerated compared to many other antiseizure medications, but patients may experience:

• Central nervous system effects:

  • Headache
  • Dizziness
  • Somnolence
  • Insomnia 3

• Gastrointestinal effects:

  • Nausea
  • Constipation
  • Dry mouth 4

• Other common effects:

  • Infection
  • Fatigue 5

Serious Side Effects

Dermatological Reactions

• Skin rash: Occurs in approximately 5.1% of adult patients 2

  • Most rashes develop during the initial titration phase
  • Risk factors include:
    • Co-medication with valproate (9.1% risk)
    • Higher initial doses and rapid dose escalation
    • History of allergies 2, 5

• Severe cutaneous reactions:

  • Stevens-Johnson syndrome (0.4% of cases)
  • To minimize risk, lamotrigine dosage should be titrated slowly over a 6-week period 6, 2

Psychiatric Side Effects

• Mood-related effects:
  • Affective switches (mania/hypomania)
  • Acute psychotic episodes
  • Hallucinations 7

Cognitive Effects

Unlike many other antiseizure medications, lamotrigine has a favorable cognitive profile:

• No significant impairment of arousal function

• No significant impairment of sensory-perceptual functions

• No significant impairment of cognitive functions 4

• Driving performance is generally not impaired with continued administration 4

• Processing speed is generally preserved compared to traditional antiseizure medications 3

Weight Effects

An important advantage of lamotrigine is that it does not appear to cause weight gain, unlike many other medications used for epilepsy or bipolar disorder 6.

Long-Term Safety

• Long-term use of lamotrigine is generally well-tolerated, even at high maintenance doses 5
• After the initial titration phase, discontinuation due to adverse effects is uncommon
• Monitoring of serum levels is generally not required unless there are specific concerns 3

Drug Interactions

Lamotrigine levels can be affected by other medications:

• Decreased by:

  • Enzyme inducers (carbamazepine, phenytoin)
  • Rifamycins
  • Oral contraceptives

• Increased by:

  • Valproate 3

Monitoring and Management

• Slow titration is crucial to minimize risk of rash (starting at low doses and gradually increasing)
• Patients should be educated to report any skin reactions immediately
• For mild allergic skin reactions, some patients can continue treatment with concomitant anti-allergic medications 2
• Monitor for any psychiatric symptoms, particularly in patients with bipolar disorder 7

Lamotrigine's side effect profile compares favorably to many traditional antiseizure medications, with the primary concern being skin rash during the initiation phase.