Tigecycline is a semi-synthetic tetracycline prepared by the introduction of a tert-butylaminoacetamido group into a previously unexplored and unsubstituted region of existing tetracyclines. Like other tetracyclines, tigecycline acts by reversibly binding to the 30S ribosomal subunit and inhibits protein translation by blocking entry of aminoacyl-tRNA into the ribosome A site. The enhanced activity can be attributed to stronger binding affinity, thus minimising the impact of existing mechanisms of resistance. Tigecycline is regarded as the first of a new class of glycylcyline antibiotics. Critical comparison to the tetracycline class appears to be lacking in the literature.