Lamotrigine
Examples
Lamotrigine
Indications
Lamotrigine has a relatively broad spectrum of use, and is commonly used to treat partial and generalised seizures.
Contraindications
Contraindications
The only direct contraindication to taking Lamotrigine is hypersensitivity to the drug itself, and this, combined with the fact that it is effective against so many types of seizure, makes it an attractive anti-epileptic to prescribe.
Caution
Despite direct hypersensitivity being the only absolute contraindication, it is important to use caution when prescribing Lamotrigine to patients with renal failure, and for those with hepatic failure, the dose may need to be adjusted significantly by a specialist.
Mechanism
Lamotrigine acts as a sodium channel blocker, to reduce the influx of sodium ions into neurones, and therefore reduced action potentials. This effectively stops the neurones from repetitively "firing" and therefore prevents seizures.
Administration
Lamotrigine is administered orally.
Adverse Reactions
The most commonly reported side effects of Lamotrigine are:
- Rashes
- Nausea, vomiting and diarrhoea
- Somnolence or insomnia
- Headache
- Dizziness
- Blurred vision or diplopia
- Ataxia
As with numerous other anti-epileptics, severe dermatological side effects are an important but rare potential side effect of Lamotrigine treatment. Lamotrigine is therefore started at a low dose and slowly increased. Slow drug introduction is a disadvantage to patients who require urgent treatment.
Other rare but important side effects are:
- Hypersensitivity syndrome (fever, lymphadenopathy, facial oedema, abnormalities of the blood and liver, disseminated intravascular coagulation, multi-organ failure)
- Haematological abnormalities
Interactions
Compared to other anti-epileptics Lamotrigine has very few drug interactions with other drug classes. However, it has been shown to interact with other anti-epileptics, which can cause potential problems.
Lamotrigine's half-life has been shown to be reduced by both carbamazepine and phenytoin, due to their induction of liver enzymes involved in the metabolism of Lamotrigine. Conversely, when Sodium Valproate is prescribed along with Lamotrigine, the half-life of lamotrigine is increased and in clinical practice a smaller dose of lamotrigine is prescribed if a patient is also being given valproate.
Education
As with any anti-epileptics, patients should be reminded about the importance of contacting the DVLA (Medical Standards of Fitness to Drive) and should be firmly warned not to abruptly stop taking Lamotrigine as this can cause serious withdrawal seizures. In the majority of cases, patients should be slowly withdrawn over a two week period, and the decision to stop Lamotrigine abruptly should be made by a specialist neurologist.
Pharmacokinetics
Nil relevant.
