The present invention relates to hitherto unknown compounds of formula (I) or their tautomeric forms, the attachment to the pyridine ring being in the 3- or 4-position, in which formula R.sub.1 stands for one or more substituents which can be the same or different and are selected from the group consisting of: hydrogen, halogen, trifluoromethyl, carboxy, C.sub.1 -C.sub.4 alkyl, alkoxy or alkoxycarbonyl, nitro, amino or cyano and Q stands for C.sub.9 -C.sub.20 divalent hydrocarbon radical which can be saturated, straight or branched or Q stands for C.sub.4 -C.sub.20 divalent hydrocarbon radical which can be cyclic or unsaturated and X stands for oxygen, sulfur or nitrogen the latter optionally being substituted by hydrogen or C.sub.1 -C.sub.4 alkyl and R.sub.2 stands for one or more substituents which can be the same or different and are selected from the group consisting of: hydrogen, C.sub.1 -C.sub.4 alkyl or alkoxy, hydroxy, halogen, trifluoromethyl, cyano, carboxamido, sulfamoyl or nitro; and pharmaceutically acceptable, non-toxic salts and N-oxides thereof. The present compounds are of value in the human and veterinary practice. ##STR1##