
Pseudomembranous colitis has been reported with nearly all antibacterial agents, including erythromycin, and may range in severity from mild to life-threatening. Therefore, it is important to consider this diagnosis in patients who present with diarrhea subsequent to the administration of antibacterial agents.
Treatment with antibacterial agents alters the normal flora of the colon and may permit overgrowth of clostridia. Studies indicate that a toxin produced by Clostridium difficile is one primary cause of “antibiotic-associated colitis”.
After the diagnosis of pseudomembranous colitis has been established, therapeutic measures should be initiated. Mild cases of pseudomembranous colitis usually respond to drug discontinuation alone. In moderate to severe cases, consideration should be given to management with fluids and electrolytes, protein supplementation and treatment with an antibacterial drug clinically effective against C. difficile colitis.
There is currently no manufacturer warning information available for this drug.
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%.