Spiramycin is belonged to antibiotics, Spiramycin acts on the bacterial protein synthesis by binding reversibly to the 50S subunit of the ribosome, the spectrum of activity of spiramycin is extended to Gram+ve organisms ( streptococcus, staphylococcus) , Mycoplasma (Mycoplasma spp ) and a few gram-ve (Mannheimia haemolytica , pasteurella multocida) with tissue tropism for the lung higher than the blood.