GENERIC NAME: lamotrigine

BRAND NAME: Lamictal

DRUG CLASS AND MECHANISM: Lamotrigine is an oral drug that is used 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.

PRESCRIPTION: yes

GENERIC AVAILABLE: no

PREPARATIONS: Tablets: 25 mg (white), 100 mg (peach), 150 mg (cream), and 200 mg (blue)

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

PRESCRIBED FOR: Lamotrigine is used in combination with other anti-seizure drugs in the treatment of some types of seizures. It also is used alone for treating partial seizures in patients 16 years and older when converting from the anti-epileptic drug valproate.

DOSING: The initial dose of lamotrigine in patients not taking valproic acid (Depakote) is 50 mg once daily for two weeks, followed by 100 mg daily given in two divided doses for two weeks. Thereafter, the usual maintenance dose is 300 to 500 mg daily given in two divided doses. In patients taking valproic acid, the initial dose of lamotrigine is 25 mg every other day for two weeks, then 25 mg once daily for two weeks, slowly increasing the dose (by 25 to 50 mg per day) every one to two weeks) until a dose of 100 to 150 mg daily is reached. Standard doses of lamotrigine are given twice daily.

DRUG INTERACTIONS: Lamotrigine can interact with valproic acid. When lamotrigine is begun 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. 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.

PREGNANCY: Damage to the fetus has been shown in some but not all pregnant animal species given lamotrigine. There have been no good studies in pregnant women. Physicians may choose to prescribe lamotrigine to pregnant women if they feel the benefit outweighs the potential risk.

NURSING MOTHERS: Lamotrigine is secreted into human breast milk. Because the effects on the infant are unknown, breast-feeding while taking lamotrigine is not recommended.

SIDE EFFECTS: Severe, life-threatening rashes have occurred with lamotrigine. The risk in children (for whom lamotrigine is not approved) is as high as 1 in 50 to 1 in 100 patients. Rash is rare in adults, but the risk is increased if the dose is increased faster than recommended or if patients also are taking valproic acid. Nearly all reported rashes have occurred within 2 to 8 weeks of starting therapy. Patients taking lamotrigine should report any rash to a physician immediately.

Severe liver disease has been reported with lamotrigine rarely (less than 1 per 1000 patients).

As a general rule, anti-seizure medicines 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.

The most commonly noted side effects reported by patients taking lamotrigine (in combination with other anti-seizure medicines) are dizziness, somnolence, headache, double vision, blurred vision, nausea, vomiting and rash.

Antiepileptic medications have been associated with increased risk of suicidal thinking and behavior. Anyone considering the use of antiepileptic drugs must balance this risk of suicide with the clinical need. Patients who are started on therapy should be closely observed for clinical worsening, suicidal thoughts, or unusual changes in behavior.

Pharmacy Author: Emmanuel Saltiel, Pharm. D.
Medical Editor: Jay M. Marks, M.D.

Last Editorial Review: 11/26/2001 3:59:00 PM

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