The delayed effect of sodium valproate on the photoconvulsive response in man.

The acute effect of a single oral dose of sodium valproate on the photoconvulsive response has been studied. In 7 of 9 patients naive to this drug photosensitivity was abolished or reduced. A similar effect was seen in only 2 of 7 already receiving chronic sodium valproate therapy. The effect appeared 1 to 5 hr (mean, 3 hr) after attainment of peak sodium valproate concentration and lasted up to 5 days.