Abstracts

Pharmacological tolerance is predominantly associated with benzodiazepine drug therapy. In levetiracetam there are several experimental datas, which support the suggestion of pharmacological tolerance in this drug. To carry out clinical evidence for this phenomenon is difficult, but nevertheless the course of clinical treatment many times let rise the question, whether the loss of efficacy in this drug is related to the development of tolerance. In this study we analyzed the different factors of secondary inefficacy and the contribution of tolerance to this effect.
We analyzed retrospectively the patient charts from 205 patients under levetiracetam therapy. The seizure frequency was established by the personal diary of the patients. Secondary inefficacy was analized in the group of patients, which had a minimum of 50 % improvement in seizure frequency under levetiracetam
From 205 patients under levetiracetam we had 107 (52%) responder. From these 107 responder 34 (32%) showed secondary inefficacy. The detailed analysis of the 34 patients with supposed secondary inefficacy showed the follow results: 17 had a change in the basic medication, indicating a primary inefficacy of levetiracetam. 8 cases where shown as observational artefacts. 4 cases had non-compliance and only 5 cases had suggested development of tolerance. That indicates, that only 4.8 % of the responder had the suggestion of tolerance. These cases showed typical aspects of tolerance e.g. with renewed improvement of seizure control after elevation of the drug-dosage.
The verification of drug tolerance in clinical settings is difficult to verify. The subanalysis of secondary inefficacy showed, that only 4.8 % of responder-patients are supposed to develop tolerance. This shows the need for detailed analysis of the therapeutical course before diagnosing drug tolerance.