Psychotropic deuterated derivatives of phenylhydantoin and pharmaceutical compositions comprising such derivatives

A psychotropic pharmaceutical composition, which comprises as an active constituent, a therapeutically effective amount of a deuterated phenylhydantoin corresponding to the formula ##STR5## wherein R.sub.1, which may be the same or different, represents hydrogen or methyl, R.sub.2 is ethyl, unsubstituted phenyl or phenyl substituted by halogen, straight chain or branched chain alkyl comprising 1 to 4 carbon atoms, straight or branched chain alkoxy comprising 1 to 4 carbon atoms, trifluoromethyl, nitro or amino, which phenyl or substituted phenyl may be deuterated, R.sub.3 is hydrogen, halogen, straight chain or branched chain alkyl comprising 1 to 4 carbon atoms, straight or branched chain alkoxy comprising 1 to 4 carbon atoms, trifluoromethyl, nitro or amino, X is oxo, thio or methylene and x is an integer, with the proviso that the deuteration in R.sub.2 and due to d.sub.x is such that said deuterated phenylhydantoin corresponding to the formula (I) is a mono- or penta-deuterated phenylhydantoin, one of its enantiomers or one of its salts with a physiologically acceptable base, in combination with a pharmaceutically acceptable vehicle.