LAMOTRIGINE

Mechanism of Action :

Lamotrigine inhibits voltage-sensitive sodium channels, thereby stabilising neuronal membranes and consequently inhibiting pathological release of excitatory amino acids (e.g. glutamate and aspartate). These amino acids play a role in the generation and spread of epileptic seizures.

Indication, Dosage and Frequency :


Oral
MONOTHERAPY IN EPILEPSY
Adult: Initially, 25 mg once daily for 2 wk followed by 50 mg once daily for 2 wk; thereafter, increase the dose by a max of 50-100 mg every 1-2 wk to usual maintenance doses of 100-200 mg daily, as a single dose or in 2 divided doses. Some patients may require up to 500 mg daily.
Child: >12 yr: Initially, 25 mg once daily for 2 wk followed by 50 mg once daily for 2 wk; thereafter, increase the dose by a max of 50-100 mg every 1-2 wk to usual maintenance doses of 100 -200 mg daily, as a single dose or in 2 divided doses. Some patients may require up to 500 mg daily. <12 yr: Not recommended.
Max Dosage: Adult: 500 mg daily.
ADJUNCT IN EPILEPSY
Adult: With valproate: Initially, 25 mg on alternate days for 2 wk followed by 25 mg once daily for 2 wk; thereafter, increase by a max of 25-50 mg every 1-2 wk; usual maintenance doses: 100-200 mg daily in 1-2 divided doses. With enzyme-inducing antiepileptics but not with valproate: 50 mg once daily for 2 wk followed by 50 mg bid for 2 wk; thereafter, increase by a max of 100 mg every 1-2 wk; usual maintenance doses: 200-400 mg/day in 2 divided doses; up to 700 mg/day in some patients. With oxcarbazepine but no enzyme-inducing or -inhibiting antiepileptics: 25 mg once daily for 2 wk followed by 50 mg once daily for 2 wk; thereafter increase dose by a max of 50-100 mg every 1-2 wk; usual maintenance doses: 100-200 mg daily in 1-2 divided doses; up to 500 mg daily in some patients.
Child: With valproate: Initially, 0.15 mg/kg once daily for 2 wk followed by 0.3 mg/kg once daily for 2 wk; thereafter, increase by a max of 0.3 mg/kg every 1-2 wk to usual maintenance doses of 1-5 mg/kg once daily or in 2 divided doses.
BIPOLAR DISORDER
Adult: Monotherapy: Initially, 25 mg once daily for 2 wk followed by 50 mg once daily for 2 wk; thereafter, double the daily dose at wkly intervals to usual maintenance dose of 200 mg daily. Max dose: 200 mg/day. With valproate: Initially, 25 mg every other day for 2 wk followed by 25 mg once daily for 2 wk; thereafter, double the daily dose at wkly intervals to usual maintenance dose of 100 mg daily. With enzyme-inducing antiepileptics but not with valproate: Initially, 50 mg once daily for 2 wk followed by 100 mg daily in 2 divided doses for 2 wk; thereafter, increase in 100-mg increments wkly to usual maintenance dose of 400 mg daily in 2 divided doses.

Interactions :

Metabolism enhanced by enzyme-inducing drugs e.g. phenytoin, carbamazepine, phenobarbitone, primidone, rifampicin, ethinyloestradiol/levonorgestrel combination. Metabolism reduced by sodium valproate.