Lamotrigine

Indications

Lamotrigine is used for: Epilepsy, Bipolar disorder

Adult Dose

Oral 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. 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. 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. Hepatic impairment: Moderate impairment (Child-Pugh category B): Reduce dose by about 50%. Severe impairment (Child-Pugh category C): Reduce dose by about 75%.

Child Dose

Oral Epilepsy 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. Adjunct in epilepsy 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.

Renal Dose

Renal impairment Use caution; may consider reduce the dose in significant renal impairment

Administration

May be taken with or without food.

Contra Indications

Hypersensitivity.

Precautions

Hepatic or renal impairment. Closely monitor patient. Monitor children's body wt. Advise patient to report any hypersensitivity reaction. Avoid abrupt withdrawal unless severe skin reactions have developed. May impair ability to drive or operate machinery. Pregnancy and lactation. Lactation: Distributed into human breast milk; caution advised

Pregnancy-Lactation

Interactions

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

Adverse Effects

Side effects of Lamotrigine : >10% Dizziness (38%),Diplopia (26-30%),Headache (29%),Ataxia (22%),Blurred vision (16-20%),Rhinitis (11-15%),Somnolence (14%) 1-10% Insomnia (6-10%),Fatigue (8%),Chest pain (5%),Peripheral edema (2-5%),Suicidal ideation (2-5%),Dermatitis (2-5%),Dry skin (2-5%),Increased libido (2-5%),Rectal hemorrhage (2-5%),Weakness (2-5%),Agitation (1-5%),Dysarthria (1-5%),Edema (1-5%),Fever (1-5%),Migraine (1-5%),Abnormal thoughts (1-5%),Urinary frequency (1-5%),Tremor (4%) Frequency Not Defined Palpitations,Anxiety,Chills,Depression,Decreased memory,Emotional lability,Incoordination,Malaise,Seizure exacerbation,Vertigo,Pruritus,Rash,Amenorrhea,Hot flashes,Abdominal pain,Constipation,Diarrhea,Dyspepsia,Nausea,Vomiting,Arthralgia,Neck pain,Cough,Flu syndrome,Infection,Vaginitis,Nystagmus Potentially Fatal: Stevens-Johnson syndrome and toxic epidermal necrolysis.

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.