LAMOTRIGINE - A NEW ANTIEPILEPTIC DRUG

Lamotrigine (Lamictal(R)) was registered in Germany in 1993 for use as an antiepileptic add-on drug. Lamotrigine is a triazine-derivative and inhibits repetitive discharges through prolonged inactivations of neuronal membrane sodium channels similar to the action of phenytoin and carbamazepine. In addition, lamotrigine blocks the release of both the excitatory neurotransmitter glutamate and the inhibitory neutrotransmitter gamma-butyric-acid. Enzyme inducing antiepileptic drugs such as carbamazepine, phenytoin or phenobarbital increase the clearance while valproate will inhibit the clearance of lamotrigine. As a consequence the initial dose of lamotrigine is very small in patients receiving valproate otherwise adverse reactions e. g. rashes may increase. Monitoring of the plasma concentration of lamotrigine may be required due to the interactions. Adding lamotrigine (100-300 mg per day) will reduce the seizure frequency by at least 50% in 23% of patients with previously uncontrolled partial seizures. Approximately 2-7% of the patients will achieve complete seizure control. Preliminary clinical observations suggest that lamotrigine may be also effective to a hitherto undetermined extent for the treatment of generalized seizures e. g. atypical absence, atonic or myoclonic seizures. The tolerability of lamotrigine is altogether good. The rash rate is similar to that for phenytoin or carbamazepine. In 1 out of 1000 patients a potentially life-threatening Stevens-Johnson-Syndrome or Lyell-Syndrome occur which will require immediate discontinuation of lamotrigine.