Lamotrigine

Lamotrigine(中文:拉莫三嗪) is an anticonvulsant medication used to treat epilepsy and to delay or prevent the recurrence of depressive episodes in bipolar disorder. Lamotrigine is FDA-approved therapy for the form of epilepsy known as Lennox-Gastaut syndrome. It reduces the frequency of seizures.

Pronunciation

Lamotrigine 50mg

Drug Names

Generic Name 藥名	HA Code 藥物代碼	Classification藥物分類
Lamotrigine Tablet 50mg	LAMO01	P1S1S3

Mechanism of Action

Anticonvulsant medication. It inhibits the sodium channels leading to stabilization of neuronal membrane

Dosage

Epilepsy

By mouth as monotherapy the initial oral dose for use as monotherapy is 25 mg once daily for 2 weeks followed by 50 mg once daily for 2 weeks; thereafter the dose is increased by a maximum of 50 to 100 mg every 1 to 2 weeks to usual maintenance doses of 100 to 200 mg daily in 1-2 divided doses. As adjunct to therapy but not taking valproate, the dosage regime is as for monotherapy. In those taking valproate, the initial oral dose of lamotrigine is 25 mg every other day for 2 weeks followed by 25 mg once daily for 2 weeks; thereafter the dose is increased by a maximum of 25 to 50 mg every 1 to 2 weeks to usual maintenance doses of 100 to 200 mg daily in 1-2 divided doses.

Bipolar disorder

Monotherapy without valprate:	initially 25 mg once daily for 14 days, then
	50 mg daily in 1-2 divided doses for further 14 days, then
	100 mg daily in 1-2 divided doses for further 7 days.
	Usual maintenance 200 mg daily in 1-2 divided doses
	Max. 400 mg daily
Adjunctive therapy with valproate:	initially 25 mg on alternate days for 14 days, then
	25 mg once daily for further 14 days, then
	50 mg daily in 1-2 divided doses for further 7 days;
	Usual maintenance 100 mg daily in 1-2 divided doses;
	Max. 200 mg daily

Administration in children

*2-12 years:	initially 300 micrograms/kg daily in 1-2 divided doses for 14 days, then
	600 micrograms/kg daily in 1-2 divided doses for further 14 days, thereafter
	Increased by max. 600 micrograms/kg every 1-2 weeks.
	Usual maintenance 1-10 mg/kg daily in 1-2 divided doses.
	Max. 200 mg daily.

The use and doses of lamotrigine in children over 12 years of age is as for adults.

Side Effects

Adverse drug reactions associated with the use of pregabalin include:

Very Common (>10% of people with lamotrigine)	Dizziness, drowsiness
Common (1-10% of people with lamotrigine)	Blurred vision, diplopia, Ataxia Aggression Agitation Back pain Tremor Nausea and vomiting
Rare (<0.1% of people with lamotrigine)	Blood disorders, anaemia, leucopenia Exacerbation of Parkinson’s disease Hallucination Hepatic failure Hypersensitivity syndrome Lupus erythematosus-like reactions

Lamotrigine binds to the eye and melanin-containing tissues which can accumulate over time and may cause toxicity. Prescribers should be aware of the possibility of long-term ophthalmologic effects and base treatment on clinical response.

Serious skin reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis have developed; most rashes occur in the first 8 weeks of start of therapy.

Pharmacokinetics

Oral bioavailability	Lamotrigine is rapidly absorbed after oral doses.
Onset of action	Peak plasma concentrations occur about 2.5 hours after oral doses.
Metabolism	It is extensively metabolized in the liver
Elimination half-life	It is excreted almost entirely in urine. The mean elimination half-life is about 24 to 35 hours.

Drug Management

Monitoring

• Lamotrigine binds to the eye, should monitor long-term ophthalmologic effects
• Liver and kidney function tests to monitor side effects
• Symptoms and signs suggestive of bone-marrow failure, such as anaemia, bruising or infection.
• Patients with heart failure should be weighed regularly to detect fluid retention.
• Patients with pre-existing cardiac conduction disorders should be carefully monitored.
• changes in mood, the development or worsening depression, and/or any thoughts or behaviour of suicide.

Drug interaction

There are complex interactions between antiepileptics, and toxicity may be enhanced. Plasma monitoring is often advisable with combination therapy. The metabolism of lamotrigine is enhanced by the enzyme inducers carbamazepine, phenytoin, and phenobarbitone, and inhibited by valproate.

Caution

• Avoid abrupt withdrawal (taper off over 2 weeks or longer) unless serious skin reaction occurs
• Parkinson’s disease (may be exacerbated)

Hepatic impairment

halve dose in moderate impairment; quarter dose in severe impairment

Renal impairment

Caution in renal failure; metabolite may accumulate; consider reducing maintenance dose in significant impairment

Pregnancy

Women of child-bearing potential should discuss with a specialist the impact of both epilepsy, and its treatment, on the outcome of pregnancy. There is an increased risk of teratogenicity associated with the use of antiepileptic drug (especially if used during the first trimester)

Breast-feeding

Use during breast feeding is not recommended.

Epilepsy and driving

Driving by patients with epilepsy is generally regulated. Also, antiepileptic drugs may produce CNS-related adverse effects, including dizziness and drowsiness, that could impair a patient’s ability to drive a vehicle or operate machinery, particularly during the initial stages of therapy.

FAQ

How should I take the tablet?

Take preferably with or after food.

What should I avoid while taking?

Avoid abruptly discontinue the medication.

What happen if I overdose?

Contact your primary care doctor. If emergency situation, call 999

What happen if I miss a dose?

Take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.