L-METHIONINE-S,R-SULFOXIMINE is a convulsant, although the susceptibility to convulsions induced by this compound depends on the species, and primates are relatively resistant. It is a methionine sulfoximine in which the amino group has S-stereochemistry. It has a role as an EC 6.3.1.2 (glutamate--ammonia ligase) inhibitor. Sub-convulsive doses of L-METHIONINE-S,R-SULFOXIMINE are neuroprotective in rodent models of hyperammonemia, acute liver disease, and amyotrophic lateral sclerosis and suggest L-METHIONINE-S,R-SULFOXIMINE may be clinically useful. Studies have also indicated that L-METHIONINE-S,R-SULFOXIMINE is therapeutic in the treatment of glutamate excitotoxicity.