lamotrigine

Lamotrigine is an oral drug that is used primarily for treating seizures. It is chemically unrelated to other anti-seizure drugs. The precise mechanism by which lamotrigine exerts its anti-seizure action is not known. The FDA approved lamotrigine in December 1974.

Lamictal, Lamictal CD, Lamictal ODT, Lamictal XR, Lamictal Starter

GENERIC AVAILABLE: Yes

Yes

The most common side effects of lamotrigine are:

• dizziness,
• somnolence,
• headache,
• double vision,
• blurred vision,
• nausea,
• vomiting, and
• rash.

Severe, life-threatening rashes have occurred with lamotrigine. The risk of rash is increased if the dose is increased faster than recommended or if patients also are taking valproic acid. Patients taking lamotrigine should report any rash to a physician immediately.

Other important side effects include:

• increased risk of developing aseptic meningitis and
• reduced white blood cells, red blood cells, and platelets.

Multiorgan failure, including fatal liver disease rarely has been observed during lamotrigine treatment.

As a general rule, anti-seizure medications should not be abruptly stopped because of the possibility of increasing the frequency of seizures. In most cases, the dose of lamotrigine should be gradually lowered over a period of at least two weeks. Antiepileptic medications have been associated with an increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need for the drugs. Patients who are started on therapy should be closely observed for clinical worsening, suicidal thoughts, or unusual changes in behavior.

The dose of immediate release lamotrigine for seizures in patients not taking valproic acid (Depakote, Depakote ER, Depakene, Depacon, Stavzor), but taking seizure medications that reduce lamotrigine blood levels (for example, phenobarbitol, phenytoin [Dilantin, Dilantin-125], carbamazepine [Tegretol], primidone) is 50 mg once daily for two weeks, followed by 100 mg daily given in two divided doses for two weeks. Thereafter, the dose is increased by 100 mg daily every 1-2 weeks up to the usual maintenance dose of 300 to 500 mg daily given as a divided dose.

In patients who are taking valproic acid in which it increases blood levels of lamotrigine, the initial dose of lamotrigine is 25 mg every other day for two weeks, then 25 mg once daily for two weeks. After 4 weeks the dose is slowly increased by 25 to 50 mg per day every one to two weeks until a dose of 100 to 400 mg once daily or divided twice daily is reached. The maintenance dose when using extended release tablets is 200 to 600 mg once daily.

The target dose for treating bipolar disorder is 100 to 400 mg daily.

Lamotrigine can interact with valproic acid. When lamotrigine is initiated in patients already receiving valproic acid, the blood concentrations of valproic acid can decrease over a 3-week period. This may result in loss of seizure control. Valproic acid increases lamotrigine levels. The risk of severe skin rash may be increased by combining lamotrigine with valproic acid. There may be a higher incidence of dizziness, double vision, and blurred vision in patients receiving carbamazepine together with lamotrigine. The mechanism of this interaction is unclear.

Estrogen containing oral contraceptives, phenobarbitol, primidone, phenytoin, and rifampin reduce the blood levels of lamotrigine by 40%-50% by increasing the breakdown of lamotrigine in the liver. This may result in reduced efficacy if the dose of lamotrigine is not adjusted.

Use of lamotrigine during pregnancy has not been adequately evaluated.

Lamotrigine is secreted into human breast milk. Because the effects on the infant are unknown, breastfeeding while taking lamotrigine is not recommended.

What preparations of lamotrigine are available?

• Tablets: 25, 100, 150, and 200 mg.
• Tablets, chewable (CD): 2, 5, and 25 mg.
• Tablets, orally disintegrating (ODT): 25, 50, 100, and 200 mg.
• Tablets, extended release (XR): 25, 50, 100, 200, 250, and300 mg.

How should I keep lamotrigine stored?

Tablets should be stored at room temperature, between 15 C - 30 C (59 F - 86 F).