New drug
Lamotrigine
- Aust Prescr 1994;17:6-8
- 1 January 1994
- DOI: 10.18773/austprescr.1994.013
ISSUE 1 JANUARY
Lamotrigine
Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Lamictal (Wellcome)
25 mg, 50 mg, 100 mg and 200 ing tablets
Indication: epilepsy
Lamotrigine is a phenyltriazine compound unrelated to other antiepileptic drugs. It is thought to act by inhibiting the release of excitatory neurotransmitters in the brain.
The drug is completely and rapidly absorbed from the gut. Although first pass metabolism is insignificant, the drug is extensively metabolised by the liver. The metabolites are mostly excreted in the urine. Lamotrigine has an elimination half-life of approximately 30 hours, but multiple administration may reduce the half-life by enzyme induction. Other antiepileptic drugs may affect the metabolism of lamotrigine.
Lamotrigine has been studied in patients whose seizures are not satisfactorily controlled on a single drug. Clinical trials suggest that the addition of lamotrigine will significantly reduce some patient's frequency of seizures. On the basis of these trials, the drug has been approved as an 'add-on' therapy for partial seizures. Further studies may reveal a role for lamotrigine in the treatment of other seizures.
Treatment should begin at a low dose and gradually be increased until an optimal response is obtained. The patient's other treatment may affect the dosage e.g. a lower dose is used in patients taking sodium valproate.
Most adverse effects occur during the first weeks of treatment with lamotrigine. Commonly observed adverse effects include skin rashes, dizziness, headache, diplopia, ataxia, somnolence and nausea.
