LAMOTRIGINE PLASMA-CONCENTRATIONS IN CHILDREN AND ADULTS - INFLUENCE OF AGE AND ASSOCIATED THERAPY

The effects of age and concomitant treatment on plasma lamotrigine (LT G) concentration/dose (C/D) ratios were retrospectively evaluated on 4 82 consecutive routine LTG determinations from 106 chronically-treated patients with epilepsy (40 children and adolescents aged younger than 16 years, and 66 adults aged 17 to 62 years), A linear dose/level rel ationship was observed in individual patients but not in the cumulativ e analysis, which failed to show any correlation between the administe red LTG dose and plasma concentrations. In the adult group, there were no correlations between the administered LTG dose and plasma concentr ations. Associated antiepileptic therapy affected the LTG concentratio n/dose ratio, which was significantly higher in the patients receiving valproic acid (3.4 +/- 2.0, n = 23) and significantly lower in those treated with enzyme-inducing antiepileptic drugs (0.6 +/-: 0.5, n = 57 ) than in the patients receiving valproic acid in combination with enz yme-inducing antiepileptic drugs? ethosuximide, vigabatrin, or clobaza m (1.9 +/- 1.6, n = 26). The LTG CID ratios significantly increased wi th increasing plasma valproic acid concentrations, and significantly d ecreased with increasing phenytoin concentrations. The effect of enzym e-inducing antiepileptic drugs increased with the number of associated drugs. A clear age effect was demonstrated in the homogeneously treat ed subgroups, in all of which adults had higher C/D ratios than childr en.