Tigecycline is the first glycylcycline that became available for clinical use and is a member of the tetracycline family. The chemical name for tigecycline is (4S,4aS,5aR,12aS)-9-[2- (tert-butylamino)acetamido]-4,7-bis(dimethylamino)- 1,4,4a,5,5a,6,11,12a-octahydro-3,10,12,12a-tet-rahydroxy- 1,11-dioxo-2-naphthacenecarboxamide. The empirical formula is C29H39N5O8 and the molecular weight is 585.65. Tigecycline is a semisynthetic derivative of minocycline; it has a glycylamido moiety attached to the C-9 position of minocycline (Sum et al., 1994; Hunter and Castaner, 2001). The molecular structure is shown in Figure 70.1. Tigecycline is produced by Wyeth under the trade name Tygacil.