
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.
Erythromycin Pledgets, USP contains erythromycin ((3R*,4S*,5S*,6R*,7R*,9R*,11R*,12R*,13S*,14R*)-4-[(2,6-Dideoxy-3-C-methyl-3-O-methyl-α–⌊-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), for topical dermatologic use. Erythromycin is a macrolide antibiotic produced from a strain of Saccharopolyspora erythraea (formerly Streptomyces erythreus).
It is a base and readily forms salts with acids. Chemically, erythromycin is C37H67NO13. It has the following structural formula:

Erythromycin has the molecular weight of 733.94
It is a white powder, is freely soluble in alcohols, acetone, chloroform, acetonitrile, ethyl acetate, and moderately soluble in ether, ethylene dichloride and amyl acetate. Erythromycin pledgets, USP are absorbent pads impregnated with Erythromycin Topical Solution 2%. Each pledget contains 1 mL of Erythromycin Topical Solution 2% and each 1 mL of Erythromycin Topical Solution 2% contains 20 mg of erythromycin base in a vehicle consisting of alcohol (71.5% v/v) and propylene glycol. May contain anhydrous citric acid and/or alcohol to adjust pH.