Drug information of Lamotrigine

Lamotrigine

Drug group: Anticonvulsants

Lamotrigine is an anti-epileptic medication, also called an anticonvulsant. Lamotrigine is used either alone or in combination with other medications to treat epileptic seizures in adults and children. Lamotrigine is also used to delay mood episodes in adults with bipolar disorder (manic depression).

Mechanism of effect

The precise mechanism(s) by which Lamotrigine exerts its anticonvulsant action are unknown. One proposed mechanism of action of Lamotrigine involves an effect on sodium channels.

Pharmacodynamic

Lamotrigine inhibits sodium currents by selectively binding to the inactivated state of the sodium channel and subsequently suppresses the release of the excilatory amino acid, glutamate.

Pharmacokinetics

Lamotrigine is rapidly and completely absorbed after oral administration with negligible first-pass metabolism (absolute bioavailability is 98%). The bioavailability is not affected by food. Peak plasma concentrations occur anywhere from 1.4 to 4.8 hours following drug administration. Half life: 25 +/- 10 hours (healthy individuals).

Dosage

Usual Adult Dose for Seizure Prophylaxis Added to an Antiepileptic Drug Regimen Containing Valproic Acid: Weeks 1 and 2: 25 mg every other day Weeks 3 and 4: 25 mg every day Usual maintenance dose: 100 to 400 mg/day (1 or 2 divided doses). To achieve maintenance, doses may be increased by 25 to 50 mg/day every 1 to 2 weeks. The usual maintenance dose in patients adding lamotrigine to valproic acid alone ranges from 100 to 200 mg/day. Added to Enzyme-Inducing Antiepileptic Drugs (Without Valproic Acid) Weeks 1 and 2: 50 mg/day Weeks 3 and 4: 100 mg/day in two divided doses Usual maintenance dose: 300 to 500 mg/day (in two divided doses). To achieve maintenance, doses may be increased by 100 mg/day every 1 to 2 weeks. For patients receiving enzyme-inducing AEDs but not valproate: Initial dose: 50 mg orally once a day for 2 weeks, then increase to 50 mg orally twice a day for 2 weeks. Maintenance dose: 150 to 250 mg orally twice a day. Dose may be increased by 100 mg/day every week. Maintenance doses as high as 700 mg/day have been used.

Alerts

1- Rash, Multiorgan Hypersensitivity Reactions, Blood Dyscrasias, and Organ Failure, Suicidal Thinking and Behavior, Worsening of Seizures, Central Nervous System Adverse Effects, Aseptic Meningitis may occure. 2- Use with caution and consider lower maintenance doses on patients with renal dysfunction and hepatic dysfunction.

Points of recommendation

1- Patients should be advised to notify their physician if they stop taking Lamotrigine for any reason and not to resume Lamotrigine without consulting their physician. 2-Women should be advised to notify their physician if they plan to start or stop use of oral contraceptives or other female hormonal preparations. 3-Lamotrigine extended-release should not be chewed, crushed, or divided.

Pregnancy level

C


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