Lamotrigine

1. Introduction

Lamotrigine is an antiepileptic medication (AED) and mood stabiliser primarily used to manage epilepsy and bipolar disorder. It works by inhibiting voltage-sensitive sodium channels, stabilising neuronal membranes, and reducing excessive neuronal firing.

2. Indications

  • Approved Indications:
    • Epilepsy:
      • Focal (partial) seizures.
      • Generalised tonic-clonic seizures.
      • Lennox-Gastaut syndrome (adjunctive therapy).
    • Bipolar disorder: Maintenance treatment to prevent depressive episodes.
  • Off-Label Uses:
    • Trigeminal neuralgia.
    • Neuropathic pain.
    • Borderline personality disorder (symptom management).

3. Dosage

  • Epilepsy:
    • Adults and Children (≥12 years):
      • Initial: 25 mg once daily for 2 weeks, then 50 mg daily for 2 weeks, followed by dose escalation based on clinical response.
      • Maintenance: 100–400 mg daily, in one or two divided doses.
    • Children (2–12 years):
      • Dose depends on weight and whether adjunctive therapy is used. Typically 0.3 mg/kg/day initially, titrated to 1–15 mg/kg/day.
  • Bipolar Disorder:
    • Adults:
      • Initial: 25 mg once daily for 2 weeks, then 50 mg daily for 2 weeks, followed by titration to 100–200 mg daily.
    • Elderly:
      • Start with lower doses and titrate slowly.
  • Dose Adjustments:
    • Reduced dose required if taken with valproate (due to interaction).
    • Increased dose needed with enzyme inducers (e.g., carbamazepine, phenytoin).

4. Administration

  • Take orally, with or without food.
  • Tablets should be swallowed whole or chewed (if chewable formulation is used).
  • Consistency with timing is essential to maintain stable blood levels.

5. Forms Available

  • Tablets: 25 mg, 50 mg, 100 mg, 200 mg.
  • Dispersible/chewable tablets: 2 mg, 5 mg, 25 mg.

6. Side Effects

6.1. Common Side Effects

  • Dizziness.
  • Headache.
  • Nausea or vomiting.
  • Insomnia.

6.2. Less Common Side Effects

  • Blurred vision or diplopia.
  • Skin rash (mild).
  • Tremors.

6.3. Rare but Serious Side Effects

  • Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN).
  • Aseptic meningitis.
  • Severe hypersensitivity reactions (e.g., drug reaction with eosinophilia and systemic symptoms – DRESS).
  • Suicidal ideation.

7. Warnings

  • Skin Reactions: Risk of severe rashes (e.g., SJS/TEN) is higher with rapid dose escalation or use in children. Discontinue if rash appears.
  • Suicidality: Monitor for suicidal thoughts or behaviours in patients.
  • Valproate Interaction: Increases lamotrigine levels significantly, requiring dose adjustments.

8. Precautions

  • Use cautiously in patients with:
    • Hepatic impairment.
    • Renal impairment.
    • Depression or psychiatric conditions (monitor for mood changes).
  • Avoid abrupt discontinuation to prevent rebound seizures or mood destabilisation.

9. Interactions

  • Drug-Drug Interactions:
    • Valproate: Increases lamotrigine levels (reduce dose).
    • Enzyme inducers (e.g., carbamazepine, phenytoin): Decrease lamotrigine levels (increase dose).
    • Hormonal contraceptives: Reduce lamotrigine levels; additional dose adjustments may be needed.
  • Drug-Food Interactions:
    • None significant.

10. Monitoring Parameters

  • Seizure frequency and severity (for epilepsy).
  • Mood stability (for bipolar disorder).
  • Skin examination for rashes.
  • Liver function tests (in patients with hepatic impairment).

11. Use in Children

  • Approved for epilepsy in children ≥2 years and for bipolar disorder in children ≥18 years. Dose adjustments are weight-based.

12. Use in Pregnancy

  • Category C: Can be used if benefits outweigh risks. Lamotrigine levels decrease during pregnancy due to increased clearance, so dose adjustments may be needed.
  • Monitor for congenital malformations (low risk).

13. Use in Elderly

  • Safe for elderly patients but requires cautious dose titration due to slower drug clearance.

14. Use in Kidney Disease

  • Dose adjustments may be required in moderate to severe renal impairment due to altered clearance of the drug and its metabolites.

15. Use in Liver Disease

  • Use cautiously in mild to moderate hepatic impairment. Reduce the maintenance dose by 50%–75% in severe hepatic impairment.

16. Patient Counselling Points

  • Take lamotrigine exactly as prescribed and do not miss doses.
  • Report any skin rash, fever, or flu-like symptoms immediately, as these may indicate a serious reaction.
  • Do not stop taking lamotrigine suddenly; taper the dose as advised by your doctor.
  • Inform your doctor if you become pregnant, as dose adjustments may be required.
  • If using hormonal contraceptives, discuss potential dose changes with your doctor.
  • Avoid activities requiring alertness (e.g., driving) if you experience dizziness or drowsiness.

17. Table of Brand Names, Manufacturers, and Prices

Brand NameManufacturerPrice (USD)
LamictalGSK$100–150 (30 tablets, 100 mg)
Generic LamotrigineVarious manufacturers$15–50 (30 tablets, 100 mg)

18. FAQs (15 Questions)

  1. What is lamotrigine used for?
    It is used to treat epilepsy and as a mood stabiliser in bipolar disorder.
  2. How does lamotrigine work?
    It reduces excessive neuronal firing by inhibiting sodium channels, stabilising brain activity.
  3. How long does it take for lamotrigine to work?
    Effects on mood may take several weeks. Seizure control usually improves within days to weeks.
  4. Can lamotrigine cause side effects?
    Yes, common side effects include dizziness, headache, and nausea. Rarely, it may cause severe skin reactions.
  5. What is the most serious side effect of lamotrigine?
    Severe skin reactions such as Stevens-Johnson syndrome or toxic epidermal necrolysis.
  6. How should lamotrigine be taken?
    Take it orally, with or without food, at the same time each day.
  7. What should I do if I miss a dose?
    Take it as soon as you remember, but skip it if it’s close to the next dose. Do not double the dose.
  8. Can lamotrigine be used during pregnancy?
    Yes, but dose adjustments are often needed due to changes in drug clearance.
  9. Does lamotrigine interact with hormonal contraceptives?
    Yes, contraceptives can lower lamotrigine levels, potentially requiring dose adjustments.
  10. Can I stop lamotrigine suddenly?
    No, sudden discontinuation can cause withdrawal seizures or mood destabilisation.
  11. Is lamotrigine safe for children?
    Yes, it is approved for epilepsy in children ≥2 years and for bipolar disorder in those ≥18 years.
  12. Can lamotrigine cause weight gain?
    Weight gain is uncommon. Some people may even experience mild weight loss.
  13. How should lamotrigine be stored?
    Store at room temperature, away from moisture and heat.
  14. Can lamotrigine cause drowsiness?
    Yes, drowsiness is a possible side effect, especially when starting treatment.
  15. Can lamotrigine be taken with other epilepsy medications?
    Yes, but dose adjustments may be required due to interactions with other antiepileptic drugs.