Effectiveness of first antiepileptic drug.

Purpose: To investigate the interaction among efficacy, tolerability, and overall effectiveness of the first antiepileptic drug (AED) in patients with newly diagnosed epilepsy.

Methods: The 470 patients were diagnosed, treated and followed up from January 1984 at a single center. Outcome was classified as seizure freedom for at least the last year or failure of initial treatment because of inadequate seizure control, adverse events, or for other reasons.

Results: Overall, 47% of patients became seizure-free with the first prescribed AED. A higher proportion (p = 0.025) of patients with symptomatic or cryptogenic epilepsy changed treatment because of intolerable side effects (17%), and a lower proportion (p = 0.007) became seizure-free (43.5%) compared with those with idiopathic epilepsy (8.5% and 58%, respectively). Most patients (83%) received carbamazepine (CBZ; n = 212), sodium valproate (VPA; n = 101), or lamotrigine (LTG; n = 78). The majority of seizure-free patients required only a moderate daily AED dose (93.1% with < or =800 mg CBZ, 91.3% with < or =1,500 mg VPA, 93.8% with < or =300 mg LTG), with commonest dose ranges being 400-600 mg for CBZ, 600-1,000 mg for VPA, and 125-200 mg for LTG. Most withdrawals due to poor tolerability also occurred at or below these dose levels (CBZ: 98%; VPA: 100%; LTG: 75%). Patients taking CBZ (27%) had a higher incidence of adverse events necessitating a change of treatment than did those treated with VPA (13%) or LTG (10%), resulting in fewer becoming seizure-free (CBZ vs. VPA, p = 0.02; CBZ vs. LTG, p = 0.002).

Conclusions: Nearly 50% of newly diagnosed patients became seizure-free on the first-ever AED, with >90% doing so at moderate or even modest dosing. Tolerability was as important as efficacy in determining overall effectiveness.