Generic Name: Lamotrigine

Brand name(s): Lamictal, Lamictal ODT, Lamictal XR

Lamotrigine is an anti-epileptic medication, also called an anticonvulsant. It works by decreasing abnormal electrical activity in the brain.

Lamotrigine is used alone or with other medications to treat seizures in people who have epilepsy. Lamotrigine is used to delay mood episodes in adults with bipolar disorder (manic depression). It is not known how lamotrigine works to delay mood episodes.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are taking this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful to people to take this medication if their doctor has not prescribed it.

Pharmacokinetics

After oral administration, lamotrigine is rapidly and almost completely absorbed. The bioavailability of lamotrigine tablets is about 98%. Lamotrigine undergoes negligible metabolism in humans. Less than 5% of a dose is recovered as metabolites in the urine. The mean elimination half-life of lamotrigine after a single dose is about 32 hours (range: 17 to 80 hours) and is unaffected by age or gender.

Steady-state trough plasma concentrations of lamotrigine are usually attained within 2 weeks of initiation or dose escalation. In controlled clinical trials, once daily dosing with immediate release lamotrigine was effective at doses between 100 mg and 400 mg/day. There was no clear evidence of dose-response relationship within this dose range.

The pharmacokinetics of lamotrigine are not affected by gender, age (between 4 and 18 years), ororal contraceptive use. The plasma clearance of lamotrigine is decreased by about 50% in patients with mild to moderate hepatic impairment and is decreased by about 75% in patients with severe hepatic impairment. Lamotrigine is eliminated from the plasma more slowly if renal function is impaired.

Lamotrigine is a weak inhibitor of CYP2C9 but does not induce metabolism via CYP enzymes. Therefore, interactions involving other drugs metabolized via these enzymes are unlikely.

Side Effects

The most common side effects of lamotrigine are:

  • headache
  • dizziness
  • double vision
  • blurred vision
  • diplopia
  • nausea and vomiting

Fatigue and somnolence were reported more frequently by patients receiving lamotrigine than placebo in the clinical trials. The incidence of these events increased with increasing dose of lamotrigine. At high doses, however, fatigue and somnolence were reported in a greater percentage of patients receiving placebo than those receiving lamotrigine.

The following adverse reactions have also been reported with the use of lamotrigine:

  • anorexia (loss of appetite)
  • ataxia (lack of muscle coordination)
  • constipation
  • diarrhea
  • dysarthria (impairment of articulation)
  • dyspepsia (indigestion)
  • nystagmus (involuntary eye movement)
  • tremor
  • uncontrollable muscle movements
  • weight loss or gain

The most serious adverse reaction associated with lamotrigine is Stevens-Johnson syndrome, a rare but potentially life-threatening skin reaction. Other serious skin reactions such as toxic epidermal necrolysis and erythema multiforme have also been reported. These reactions are often characterized by fever, rash, and/or mucosal lesions.

Dosage and Administration

The recommended starting dose of lamotrigine for patients taking valproate is 25 mg/day (range, 12.5 to 50 mg). The target dose should be achieved within 2 weeks and reached by titration over 2 weeks as follows: Week 1 – Day 1: 25 mg; Day 2: 50 mg; Week 2 – Day 3: 75 mg; Day 4: 100 mg; Following day 5 increase by 100 mg/day every week until the desired dose is reached.

For patients not taking valproate, the recommended starting dose of lamotrigine is 50 mg/day (range, 25 to 100 mg). The target dose should be achieved within 2 weeks and reached by titration over 2 weeks as follows: Week 1 – Day 1: 50 mg; Day 2: 100 mg; Following day 3 increase by 100 mg/day every week until the desired dose is reached.

The recommended maintenance dose of lamotrigine is 200 to 500 mg/day (range, 100 to 400 mg/day).

Elderly patients may be more sensitive to the adverse effects of lamotrigine. Therefore, initial and target doses should be lower in these patients.

Lamotrigine can be taken with or without food. If you miss a dose of lamotrigine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Overdose

Symptoms of lamotrigine overdose include:

  • nausea and vomiting
  • double vision
  • blurred vision
  • diplopia
  • dizziness
  • ataxia (lack of muscle coordination)
  • tremor
  • uncontrollable muscle movements

If you suspect an overdose, contact a poison control center or emergency room immediately. You can get in touch with a poison control center.

Storage

Store lamotrigine at room temperature, between 68 and 77 degrees F (20 and 25 degrees C). Store away from heat, moisture, and light. Do not store in the bathroom. Keep lamotrigine out of the reach of children and away from pets.