Use of a compound of formula I wherein R1 represents hydrogen or one or several, preferably 1 to 4, similar or different substituents in the positions 1-4 and/or 7-10, selected from halogen, preferably Br, lower alkyl/alkoxy group having not more than 4 carbon atoms, trifluoromethyl group, trichloromethyl group; and in one of the positions 7-10 R1 can be a hydroxyl group; X is a group —(CH2)n—R2, wherein R2 represents a nitrogen containing basic residue such as NH2, NHR4 or NR5R6, wherein R4, R5 and R6 independently are lower alkyl or cycloalkyl and n is an integer of from 1 to 4 and R3 represents hydrogen, lower alkyl/cycloalkyl group having not more than 4 carbon atoms, and the physiologically acceptable addition products of the compounds with acids and halogen adducts, preferably adducts with iodine, iodine monochloride or iodine monobromide, for preparing a drug for treatment of MS (multiple sclerosis).