The combination of colistin and enrofloxacin has additive action. Enrofloxacin is a synthetic, broad-spectrum antimicrobial substance, belonging to the fluoroquinolone group of antibiotics. Enrofloxacin is active against Gram-negative and Gram-positive bacteria and mycoplasmas. It is well absorbed after oral administration, and rapidly excreted in the bile and urine, mostly as enrofloxacin and the metabolite ciprofloxacin. Colistin is an antibiotic from the group of polymyxins with bactericidal action against Gram-negative bacteria, including
E. coli,
Haemophilus spp. and
Salmonella spp. It is absorbed poorly after oral administration and serum concentrations are generally undetectable in target species. Orally administered colistin is eliminated almost completely in faeces.