Change in oxcarbazepine (Trileptal(R)) formulation is associated with more side effects and higher blood concentrations

In an editorial , Marson and Chadwick review some of the evidence for the effectivity and tolerability of new drug treatments for epilepsy.1 They discuss the role of randomised clinical trials for providing data that satisfy the requirements of the licensing bodies but that do not reflect day to day clinical practice. With oxcarbazepine (Trileptal®) we recently experienced another complicating factor, a change in formulation, which may influence interpretation of results of clinical trials. Oxcarbazepine had recently been licensed in the United Kingdom and the United States but was already registered in The Netherlands in 1991. In our epilepsy centre we have had extensive clinical experience with oxcarbazepine since 1986.2 In 2001 we noticed new symptoms such as diplopia, dizziness, …