About Spiramycin Macrolide Antibiotic, Antibacterial (systemic,antiprotozoal,In toxoplasmosis, cryptosporidiosis. Mechanism of Action of Spiramycin Spiramycin is a member of macrolide antibiotic. It binds to the 50S sub unit of bacterial ribosome and inhibits translocation.ie: they: interfere with the transfer of the newly formed peptide chain from the A site to the P site and fails to expose the A site .So that A site is unable to bind with the next aminoacyl t RNA complex. This leads to premature termination of amino acid chain and there by inhibits protein synthesis. Indications for Spiramycin 1. Tonsilitis 2. Pharyngitis 3. Prostatitis 4. Toxoplasmosis 5. Urethritis 6. Skin and soft tissue infections 7. Amebiasis 8. Cryptosporidiosis