Tigecycline drug molecule. Ball-and-stick molecular model of the antibiotic, tigecycline. This drug, sold under the brand name Tygacil, is an antibiotic with activity against antibiotic-resistant bacterial infections including, but not limited to, methicillin-resistant Staphylococcus aureus (MRSA). Its chemical formula is C29H39N5O8. Atoms are represented as spheres with conventional colour coding: hydrogen (white), carbon (black), oxygen (red), and nitrogen (blue).