Veterinary preparations

Synergistic antibacterial-antiprotozoal drug compositions useful for the treatment of respiratory, gastrointestinal and urogenital infections of domestic animals comprises tiamulin hydrogen fumarate and microbiologically active organic acids, preferably oxolinic acid and nalidixic acid or a pharmaceutically acceptable water-soluble derivate thereof in a weight ratio of 1:5 to 5:1. The active components are admixed or diluted with a carrier used in veterinary therapy and formulated for oral or parenteral use.