Tilmicosin is a broad-spectrum semi-synthetic bactericidal macrolide antibiotic synthesized from tylosin. It has an antibacterial spectrum that is predominantly effective against Mycoplasma, Pasteurella and Haemophilus spp. and various Gram-positive organisms such as Staphylococcus spp. It is believed to affect bacterial protein synthesis.
Cross-resistance between tilmicosin and other macrolide antibiotics has been observed. Following subcutaneous injection, tilmicosin is excreted mainly via the bile into the faeces, with a small proportion being excreted via the urine.