Tigecycline is a glycylcycline antibiotic, a new class of antibiotics derived from tetracycline, with broad-spectrum activity. These tetracycline analogues are specifically designed to overcome two common mechanisms of tetracycline resistance, namely resistance mediated by acquired efflux pumps and/or ribosomal protection. Glycylcycline antibiotics have a similar mechanism of action as tetracycline antibiotics. Both classes of antibiotics inhibit protein translation in bacteria by binding to the 30S ribosomal subunit and blocking entry of amino-acyl tRNA molecules into the A site of the ribosome. This prevents incorporation of amino acid residues into elongating peptide chains. Tigecycline carries a glycylamido moiety attached to the 9-position of minocycline. The substitution pattern is not present in any naturally occurring or semisynthetic tetracycline and imparts certain microbiologic properties to tigecycline. Accordingly, tigecycline has demonstrated in vitro and in vivo activity against a broad spectrum of bacterial pathogens. However, the glycylcyclines appear to bind more effectively than the tetracyclines. Tigecycline was developed in response to the growing prevalence of antibiotic resistance in bacteria such as Staphylococcus aureus and Acinetobacter baumanii.