Electroencephalographic affects of an anti-inflammatory analgesic: mefenamic acid

A study of the electroencephalographic patterns observed following iv administration of increasing doses of mefenamic acid in acute experiments on curarized cats and rats and the possible modification of these effects by naloxone was carried out. Mefenamic acid produced in both species a progressive and dose-related increase of the voltage of the baseline patterns. With high doses, besides slow waves and fusiform complexes, an irritative activity with spikes and complexes of polyspikes was observed. The recovery of the basal activity was obtained within 15 min, except for the highest dose, under which the effect lasted 30 min after administration. Cats displayed a higher sensitivity than did rats. Naloxone did not modify the EEG effects of mefenamic acid, neigher in rats nor in rats. This fact suggests that the locus of action of these drugs is different. Mefenamic acid appears to act centrally with relatively short-lasting depressant effects at low doses and facilitating or stimulant effects at high doses.