Polyethylene glycol

Polyethylene glycol (PEG) is a synthetic polymer produced via polymerization of ethylene oxide molecules to make joining units of ethylene glycol by an ether linkage. PEGs are water-soluble polymers that can form hydrogen bonds in a ratio of 100 water molecules per one PEG molecule. Molecular weights of PEGs vary by time of the polymerization process and the molecular weight represents the weighted average of the individual PEG molecules. PEGs differ in their physical and chemical properties depending on their molecular weight: PEGs are liquids when molecular weights are <1000 and the molecule turns to waxy solids with increasing molecular weights. The most common preparations of PEGs include PEG 3350 and PEG 400. PEGs have various applications in many fields, ranging from medical to industrial areas. PEGs have a long history of gastroenterology: PEG 3350 is a common over-the-counter osmotic laxative used to relieve occasional constipation. PEG 3350 is also used for cleansing of the colon in preparation for colonoscopy in adults.

The rationale of using PEG in gastroenterology is due to the physical properties of the compound: its potent water-binding capacity, negligible intestinal absorption with increasing molecular mass, lack of significant toxicity, and limited intestinal enzymatic degradation or bacterial metabolism all make PEG a useful therapeutic agent for the treatment of occasional constipation and bowel cleansing for preparation in colonoscopy.