Assessment of effects of antiepileptic drugs

Pharmacological studies form an important adjunct to epilepsy monitoring and conversely long-term EEG and video recording are of value for assessing antiepileptic drug (AED) effects. Clinical estimates of the incidence of brief frequent seizures as absences is often difficult but greater reliability can be achieved by long-term monitoring of the seizures themselves or of the associated EEG discharges. There are, however, very marked spontaneous short-term fluctuations in discharge rates and the amounts of ictal epileptiform activity in short conventional EEGs rarely provide any useful index of AED action. Acute investigations are of value for assessing new AEDs or experimental methods of administration and for pharmacokinetic studies. For this purpose either spontaneous EEG discharges or photosensitivity may provide quantitative measures of antiepileptic effect. Long-term AED monitoring by means of an indwelling catheter indicates the time course of blood drug levels to be more complex and variable than might be expected from simple pharmacokinetic models. Short-term fluctuations in AED concentrations have little effect on epileptiform EEG activity or seizure control but are often responsible for intermittent side-effects. Conversely diagnostic EEG and monitoring studies may be required to classify seizures as an aid to determining appropriate medication and may explain apparent resistance to therapy, due to pseudo-seizures, reflex or self-induced epilepsy. Finally a case is presented for combined pharmacological EEG and video-monitoring in the preliminary assessment of new AEDs in order to improve the design of subsequent clinical trials.