Tulathromycin is a semi-synthetic derivative of erythromycin belonging to the ring expanded aza-erythromycins. Ring expansion improves the acid lability compared with the parent erythromycins. Tulathromycin is regarded as the first of the triamilides, structurally similar to azithromycin and having a third amino (propylaminomethylene) group on a sugar to improve absorption. This modification provides a stable mixture of Tulathromycin isomers when in aqueous solution, in a 9:1 ratio. Tulamycin A (CP-472,295 a 15-ring member) is the major component, and Tulathromycin B (CP-547,272, a 13-ring member) the minor component. It is used in animal research applicaitons, and is active against the bacteria causing bovine and swine bacterial respiratory diseases. LC-MS methods have been reported for Tulathromycin in plasma and tissue samples in cattle, swine, goats, and foals.
Tulathromycin A is soluble in ethanol and DMSO but is practically insoluble in water.