» Erythromycin Ethylsuccinate Injection is a sterile solution of Erythromycin Ethylsuccinate in Polyethylene Glycol 400, and contains 2 percent of butyl aminobenzoate and a suitable preservative. It contains the equivalent of not less than 90.0 percent and not more than 115.0 percent of the labeled amount of erythromycin (C₃₇H₆₇NO₁₃).