Neuroprotective agents based on inhibition of kainic acid neurotoxicity and compounds useful as neuroprotective agents based on inhibition of kainic acid neurotoxicity. An inhibitors of kainic acid neurotoxicity, comprising as an active ingredient a pyridothiazine derivative represented by the following general formula (I) or a pharmaceutically acceptable salt thereof, and a pyridothiazine derivative represented by the following general formula (I) or a pharmaceutically acceptable salt thereof: ##STR1## wherein symbols in the formula have the following respective meanings: the ring A: a pyridine ring; ##STR2## R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 may be the same or different and each represent a hydrogen atom or a lower alkyl, cycloalkyl, alkenyl, aryl, carboxyl or lower alkoxycarbonyl group which may have substituent(s), or are not present, with the proviso that R.sup.2 and R.sup.3 may together form a nitrogen-containing heterocyclic group which may have nitrogen atoms as another hetero atom, may be fused with a benzene ring and may have a lower alkyl group as a substituent.