Lamotrigine is almost completely absorbed after oral administration. Lamotrigine is extensively metabolized. The mean plasma half life after single dose of lamotrigine is approximately 24 hours.
AS ADJUCTIVE THERAPY IN SIMPLE PARTIAL SEIZURES AND SECODARILY GENERALISED TONIC-CLONIC SEIZURES: With enzyme-inducing antiepileptic drugs (EIAEDs); 50mg o.d for weeks 1 and 2, followed by a 100mg/day in 2 div doses for weeks 3 and 4. Maint; gradually increase by 100mg/day every 1-2 weeks to achieve 200-400mg/day i 2 div doses. with valproic acid(VPA) alone or in combination wiht other EIAEDs; 25mg every altenate day for weeks 1 & 2 followed by 25mg o.d. In weeks 3 & 4. 25-50mg/day in 2 div doses.
Renal functional impairment; Reduce the dose. Dosage titration should be slow while initiating the therapy, and similarly, a step-wise dose reduction should be followed at the time of discontinuation to prevent rebound seizures.
Lamotrigine has demonstrated its usefulness as an add-on therapy in patients with partial epilepsy and those with secondarily generalized tonic-clonic seizures. As the precise mechanism of action is not established in humans, when in vitro pharmacological studies are concentrated, it has suggested that lamotrigine inhibits voltage-sensitive sodium channels, thereby stabilizingneuronal membranes and consequently modulating presynaptic transmitter release of excitatroy amino acids (eg., glutamate & aspartate).
Phenytoin, carbamazepine, phenobarbitone and primidone: Enhance the metabolism of lamotrigine and may increase dose require ments.
Sodium valproate: Reduces the metabolism of lamotrigine. There is no evedence that lamotrigine causes clinically significant induction or inhibition of hepatic oxidative drug-metabolizing enzymes.
Effect & Precautions
Headache, asthenia, rash, nausea, dizziness, somnolence and insomnia.
Precaution: Severe skin rash including Stevens-Johnson syndrome and rarely toxic Epidermal Necrolysis has been reported in some cases. the incidence of such reaction is higher in paediatric population. Lamotrigine should be discontinued at the first sign of rashes. the risk is more in cases where (1) dose administered exceeds the recommended initial and total dialy dose (2) sodium valproate is co-administered.
Pregnancy: Use only if benefits outweigh.
Breast Feeding: Use with caution.