Photosensitivity as a model for acute antiepileptic drug studies.

A technique is described for assessing the efficacy and time course of effects of antiepileptic drugs, after a single acute dose, by means of their action on the human photo-convulsive response. The range of frequencies of intermittent photic stimulation to which the patient is sensitive (photosensitivity range) is determined in a standardized manner at hourly intervals over the course of a waking day. 82 controlled studies have established that, with the rare exceptions of patients showing a consistent circadian rhythm of photosensitivity, the photosensitivity range is stable over this time scale. A total of 72 studies have shown that representatives of all the major groups of established antiepileptic drugs, together with some experimental drugs, suppress photosensitivity following a single acute administration. By contrast barbiturates without antiepileptic action (methohexitone and quinalbarbitone) do not affect photosensitivity even in doses producing marked drowsiness. These findings suggest the technique to be a potentially useful tool for preliminary investigation of efficacy and duration of action of new potential antiepileptic drugs.