Ery 2% Pads contain erythromycin, USP for topical dermatologic use. Erythromycin is a macrolide antibiotic produced from a strain of Saccaropolyspora erythraea (formerly Streptomyces erythreus). It is a base and readily forms salts with acids.
Chemically, erythromycin is C37H67NO13. It has the following structural formula:
The chemical name for erythromycin is (3R*,4S*,5S*,6R*,7R*,9R*,11R*,12R*,13S*,14R*)-4-[(2,6-Dideoxy-3-C-methyl-3-O-methyl-α-L-ribo-hexopyranosyl)oxy]-14-ethyl-7,12,13-trihydroxy-3,5,7,9,11,13-hexamethyl-6-[[3,4,6-trideoxy-3-(dimethylamino)-β-D-xylo-hexopyranosyl]oxy] oxacyclotetradecane-2,10-dione.
Erythromycin has the molecular weight of 733.94. It is a white or slightly yellow, crystalline powder, slightly soluble in water, soluble in alcohol, in chloroform, and in ether. It is odorless or practically odorless. It has a pH range between 8.0 and 10.5 in a methanol and water solution prepared by diluting 1 volume of a methanol solution, containing 40 mg per mL, with 19 volumes of water.
Each mL of expressible liquid contains 20 mg erythromycin in a base of dehydrated alcohol, propylene glycol and citric acid to adjust pH. Each pledget is filled to contain 0.8 mL of Erythromycin Topical Solution 2%.