Polyethylene glycol as excipient

What is Polyethylene glycol ?

Polyethylene glycol (PEG) also known as Polyethylene oxide (PEO), is a versatile and widely used polymer that has found numerous applications in various industries, with pharmaceuticals being one of its prominent domains. This polyether compound is characterized by its water-soluble and biocompatible nature, making it suitable for a range of medical and pharmaceutical applications.

Composition and properties of Polyethylene glycol

Polyethylene glycol is a polyether compound with the general formula H(OCH2CH2)nOH, where n represents the average number of ethylene glycol units. PEG and PEO are both polymeric compounds, but they have some differences in terms of their molecular weight, applications, and characteristics, especially in the context of pharmaceutical use. PEGs can have a wide range of molecular weights, typically from around 200 to 20,000 Daltons. Polyethylene Oxide often has a molecular weight in the range of 100,000 to several million Daltons.


Physical Properties

  • Physical State: PEG is a colorless, odorless, and viscous liquid or solid, depending on its molecular weight.
  • Solubility: PEG is highly soluble in water and miscible with many organic solvents.

Chemical Properties

  • Hydrophilicity: PEG is hydrophilic, contributing to its water-soluble nature.
  • Reactivity: PEG is relatively inert, chemically stable, and non-toxic.

Excipient Characterization Services

Be in control of your product!

offers fast and flexible hands-on polyethylene glycol quantification and characterization services to reveal and compare hidden polyethylene glycol properties like :

the presence of potential reactive impurities or functional groups, degradation products and related substances, just like molecular weight distributions, reducing power and many other featured characteristics.

In addition, we can help users of excipients to pick the most appropriate polyethylene glycol manufacturer, select the most suitable polyethylene glycol grade for their finished dosage form, or define customized polyethylene glycol specifications to control product performance, quality and safety.
Contact us

Polyethylene glycol manufacturing

The production of polyethylene glycol involves the polymerization of ethylene oxide. This process is typically carried out using various catalysts, such as alkaline substances or acidic compounds. The choice of catalyst and reaction conditions can influence the molecular weight and properties of the resulting PEG.

Synthesis Route

The synthesis of polyethylene glycol commonly involves the following steps:

  1. Initiation: Ethylene oxide is initiated by a catalyst, typically an alkaline substance like potassium hydroxide or an acidic compound.
  2. Propagation: Ethylene oxide molecules add sequentially to the growing polymer chain.
  3. Termination: The reaction is terminated to obtain the desired molecular weight of polyethylene glycol.



Figure 1 Structural formula of polyethylene glycol

Stability and Degradation of Polyethylene Glycol

PEG exhibits excellent stability under normal storage conditions. However, factors such as temperature, pH, and the presence of specific ions can influence its stability. PEG is susceptible to oxidative degradation, which may occur over time. Proper storage conditions, including protection from light and excessive heat, are crucial to maintaining its stability.

Advantage and disadvantages of Polyethylene Glycol


  • Biocompatibility:
    PEG is widely recognized for its biocompatibility, making it suitable for use in various biomedical applications.
  • Versatility:
    PEG’s versatility allows for its use in different formulations and drug delivery systems.
  • Improved Drug Solubility:
    PEG can enhance the solubility of poorly water-soluble drugs, improving their bioavailability.


  • Oxidative Degradation:
    PEG may undergo oxidative degradation over time, impacting its stability.
  • Allergenicity:
    In some cases, individuals may develop allergies to PEG, though this is relatively rare.
  • Cost:
    The production of high molecular weight PEG can be expensive, impacting its cost-effectiveness in certain applications.

Be in control of your product!

Feel free to get in touch with our experts to quantify and characterize your polyethylene glycol and see how we can help you in making your products safe, robust and stable.

PEG Characterization Services

Excipia is an independent contract service platform that focuses on the quantification and physicochemical characterization of pharmaceutical excipients and food ingredients like PEG; as a pure substance, as a raw material or when processed into end products.

More than 25 years in the development of pharmaceutical formulations have taught us that the limited information available on an excipient Certificate of Analysis (CoA) often falls short of explaining observed product or excipient characteristics and that more in-depth knowledge of the actual chemical excipient composition is essential to meet and understand specific formulation challenges.

Over the past 15 years, Excipia analytical scientists have spent tens of thousands of hours establishing unique, specific analytical and physicochemical methods with ingenious sample preparation techniques to characterize polysaccharides and other pharmaceutical excipients.

In these years we have gained a lot of knowledge about many excipients, their properties and exact composition, the difference between batches, qualities, grades, and manufacturers, how to quantify them in medicines and how they can best be used in a formulation.

Excipia offers fast and flexible hands-on cellulose characterization services to reveal and compare hidden properties like:

    • the presence of potential reactive impurities or functional groups,
    • reducing power of excipients,
    • degradation products and related substances,
    • relative molecular weight distributions,
    • and many other excipient characteristics.

In addition, Excipia can help users of excipients to pick the most appropriate manufacturer, select the most suitable grade for their finished dosage form, or define customized cellulose specifications to control product performance, quality and safety.


Welcome to Excipia, a service platform dedicated to the composition, quality and quantity of excipients in medicines.

Discover our unique services such as quantitative excipient analysis, identification, selection or specific formulation development support. Don’t forget to check out our case studies.

Try us. Feel free to contact us using the “Contact”  button or by sending a message to Excipia@avivia.nl.

Menno Wiltink
Founder of Excipia.


Excipia, a division of Avivia BV

 Excipia as dedicated excipient knowledge platform is a division of Avivia BV, a Dutch independent specialized pharmaceutical development company that operates a hybrid business model combining CRO service activities with internal product development programs. The other complementary platforms of Avivia are Pharmaceutical R&D, Analytical R&D, and Biorelevant Dissolution Testing. For more information about Avivia and its pharmaceutical development CRO services, please visit the Avivia website.