Abstract: Ciprofloxacin and related gyrase inhibitors are tolerated well if administered intramuscularly in the form of an aqueous suspension of the betaine form having an approximate neutral pH value or in the form of an oily suspension of the betaine or salts thereof. Oily suspensions which contain the active material in water-soluble form, eventually in form of the hydrochlorides, lactates, mesilates, methanesulfonates and other salts, are capable of releasing the active compound very rapidly, particularly when the wettability of the oily carrier medium is increased by addition of interfacially surface active materials.