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Polyethylene Glycol 400

Medically reviewed by Last updated on Jun 2, 2023.

Excipient (pharmacologically inactive substance)

What is it?

Polyethylene glycol, referred to as PEG, is used as an inactive ingredient in the pharmaceutical industry as a solvent, plasticizer, surfactant, ointment and suppository base, and tablet and capsule lubricant. PEG has low toxicity with absorption into the body less than 0.5%.

PEGylation occurs when PEGs are attached to various protein medications, allowing for greater solubility for certain drugs. Examples of PEGylated medications include PEG-interferon alpha (Pegintron) and PEG-filgrastim (Neulasta). PEG is also available as a bowel prep for colonoscopy procedures and as a laxative.[1]

PEG "400" indicates that the average molecular weight of the specific PEG is 400.[2] PEG 3350 is a laxative available over-the-counter by the name of Miralax. In this case, PEG is considered an "active" ingredient, even though systemic absorption is less than 0.5%.[2]

List of medications using Polyethylene Glycol 400


  1. [1]Dave RH. Overview of pharmaceutical excipients used in tablets and capsules. Drug Topics (online). Advanstar. 10/24/2008 Accessed 08/19/2011
  2. ThermoScientific. PEG (Polyethylene Glycol) Reagents Accessed 08/19/2011

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.