Use of plasma levels for antiepileptic drug monitoring in clinical practice. Gruppo Collaborativo per lo Studio dell'Epilessia.

A multi-center survey of antiepileptic treatment was conducted in Italy on 245 previously untreated ("new") patients with epilepsy and 355 patients treated for more than three months ("old" patients). Therapeutic drug monitoring (TDM) of antiepileptic drugs was evaluated in the context of routine clinical conditions, in relation to individual therapeutic problems and mode of treatment. Plasma levels (PL) were determined in 75% of "new" patients and 78% of "old" patients, with wide intercenter variability. TDM was done at 69% of the follow-up attendences for "new" patients and at 34% for "old" patients, but was apparently unrelated to specific therapeutic problems, such as poor disease control or adverse drug reactions. Plasma drug concentration measurements were made more often among patients on polytherapy. The age of the patient and the time elapsing since diagnosis did not seem to affect request patterns significantly. From these findings it appears that TDM is largely influenced by factors unrelated to the common recommendations in the literature. In addition, the use of TDM in clinical practice reflects the limitations of the available techniques.