Abstract: The present invention relates to novel xanthene and thioxanthene derivatives of the following general formula: ##SPC1##Wherein Y represents sulfur or oxygen, R.sup.1 represents hydrogen, chlorine, trifluoromethyl or dimethylsulfamoyl, R.sup.2 represents hydrogen or fluorine; and R.sup.3 and R.sup.4 each represents hydrogen or methyl, provided that R.sup.3 and R.sup.4 may not both represent hydrogen, or R.sup.3 and R.sup.4 taken together with the nitrogen atom form a piperazine or piperidine ring optionally substituted in the 4-position by a methyl group or a 2-hydroxyethyl group, if desired, esterified with an aliphatic carboxylic acid having from 1 to 17 carbon atoms inclusive, as well as non-toxic acid addition salts thereof.