Erythromycin A 9-oxime is a semi-synthetic analog Erythromycin prepared as means of overcoming acid lability and improving oral absorption of Erythromycin A while retaining antibacterial potency. Although not developed as a commercial product, Erythromycin Oxime was pivotal in the development of the ring expanded aza-erythromycins (e.g. azithromycin) and the oxime ethers (e.g. roxithromycin).