Oxcarbazepine (OXC) is thought to have a more favourable metabolic profile than carbamazepine (CBZ) due to a relatively low potential of enzyme-inducing effects. It has been reported that replacing CBZ by OXC is associated with a decrease of gammaglutamyl- transferase (GGT). Since our clinical experiences were not in line with these observations, we investigated the impact of OXC and CBZ on clinically relevant laboratory values representing enzyme induction along with some other relevant parameters indicative for potential long-term tolerability problems such as electrolytes and blood cell measures. Lamotrigine (LTG) served as the control due to its with well documented low enzyme- induction potential. We measured 13 values (bilirubin, liver enzymes, amylase, lipase, alkaline phosphatase (AP), uric acid, urea, creatinine, sodium, potassium, calcium) in 116 adult patients (56 male and 60 female) receiving CBZ (n=55), OXC (n=27) and LTG (n=34) in monotherapy. All patients had been under stable therapy for at least 3 months without additional drug treatment. In order to exclude interfering effects resulting from previous treatment with enzyme inducing drugs we performed a second analysis with 32 OXC patients who took OXC as first (n=11) or second (n=21) monotherapy after prior treatment with a non-enzyme inducing AED, namely with valproate (VPA) (n=15) or LTG (n=6). No major differences were found between CBZ and OXC. Relevant differences were apparent when LTG was compared with CBZ or OXC. Under LTG, AP and GGT were significantly lower and calcium and leukocyte values significantly higher than with CBZ and OXC. These data suggest that the enzyme inducing effect of OXC may have been previously underestimated and in the range of CBZ. © Steinkopff-Verlag 2007.
