Polyethylene Glycol for Laxatives

Polyethylene glycol (PEG) is a widely used polymer compound formed by chemical polymerization of ethylene glycol units. Its excellent solubility, non-toxic and harmless properties, and good biocompatibility make it play an important role in drug development. PEG can be used as a drug carrier, excipient, solvent, etc., to improve the stability and bioavailability of drugs. In the application of laxatives, PEG is used as an osmotic laxative, which increases the osmotic pressure in the intestine, promotes the entry of water molecules into the intestinal cavity, helps soften the stool, increases the volume, accelerates intestinal peristalsis, and thus effectively defecates. Compared with other types of laxatives, PEG-based laxatives are milder and have fewer side effects, making them more suitable for patients with long-term constipation.

What are Laxatives?

Laxatives are a class of drugs used to relieve constipation, promote intestinal peristalsis, and aid in bowel movements. They act on the digestive system through a variety of mechanisms to increase the bulk of the stool, soften the stool, or speed up the passage of intestinal contents. Laxatives can be divided into several categories, including bulking laxatives, lubricating laxatives, stimulant laxatives, osmotic laxatives, and saline laxatives.

• Bulking laxatives, such as fiber supplements, increase the bulk and wetness of the stool by absorbing water, making it easier to pass through the intestines. Lubricating laxatives, such as mineral oil, lubricate the intestinal walls and stool, thereby reducing friction and facilitating bowel movements. Stimulant laxatives, such as senna and phenolphthalein, speed up the passage of contents by stimulating the intestinal muscles to contract.
• Osmotic laxatives, such as polyethylene glycol (Miralax) and lactulose, increase the water content of the stool by retaining water in the intestines.

Polyethylene Glycol Laxative

The working principle of PEG as a laxative is mainly based on its high hydrophilicity, which means that it can strongly bind to water molecules. This property enables PEG laxatives to retain a large amount of water in the intestine, thereby softening the stool, increasing its volume, and promoting intestinal peristalsis. In this way, PEG helps relieve constipation and improve the symptoms of difficult defecation. The application of polyethylene glycol in laxatives usually appears in the form of PEG 3350. PEG 3350 is a polyethylene glycol with a large molecular weight. It is not absorbed or metabolized by the digestive tract and acts directly and effectively in the intestine. Clinically, PEG 3350 is used to treat chronic constipation and promote preoperative intestinal cleansing, and its effect is remarkable. At standard doses, it has good safety and is not easily absorbed by the human body, so it is not easy to cause systemic side effects. In addition, PEG 3350 has good patient tolerance, which is one of the important reasons for its widespread use in laxatives. It is tasteless and odorless, and can be mixed with liquids such as water and juice as an oral solution, which is convenient to use. Compared to some traditional laxatives, PEG 3350 does not cause abdominal cramping, making it particularly suitable for patients who need long-term constipation management, including the elderly and children.

Fig. 1. Laxative polyethylene glycol.

What is Polyethylene Glycol?

Polyethylene glycol is a polymer compound made from ethylene glycol monomers by addition polymerization, with a molecular formula of H(OCH2CH2)nOH, where n represents the number of repeated ethylene glycol units. Depending on the molecular weight, polyethylene glycol can be in a liquid or solid state. Low molecular weight PEG is usually a colorless, tasteless, odorless viscous liquid, while high molecular weight PEG is a waxy solid. Polyethylene glycol has many superior physical and chemical properties. First, PEG has good water solubility and is compatible with water regardless of molecular weight to form a stable aqueous solution. Second, PEG also has good solubility in a variety of organic solvents. It has very high chemical stability and is not easily oxidized and degraded. In addition, PEG is non-toxic, has good biocompatibility, and does not cause significant immune responses. Its viscosity and lubricating properties make it widely used in a variety of industrial and medical applications.

* Polyethylene glycol for drug development:

In drug development, polyethylene glycol is widely used, especially in the field of laxatives. The main mechanism of action of PEG as a laxative is to promote water accumulation in the intestines through osmotic pressure, thereby increasing the volume and water content of the stool and helping defecation. For example, PEG-3350 (where the molecular weight is 3350) is a commonly used non-irritating laxative that is often used to treat constipation and intestinal cleansing, such as before a colonoscopy. PEG-3350 is usually provided in powder form and needs to be mixed with water before taking. It softens the stool and promotes intestinal peristalsis through water retention, making defecation easier and more natural. In addition, PEG can also be combined with other drugs to increase the solubility and stability of the drug, thereby improving the bioavailability of the drug.

Polyethylene Glycol Uses

Polyethylene glycol can be used to modify drug proteins to protect drug molecules and prolong their half-life. It can also be used as a cell fusion agent to cause the adhesion of adjacent cell membranes, and then fuse the cells into one cell. In addition, polyethylene glycol is also a food additive, often used in candy and chocolate product coating. In food, it can be used as a coating agent, and can also be used as a dispersant, carrier solvent, adhesive, plasticizer, coating agent, lubricant, and flavoring agent. PEG 400 is most suitable for soft capsules. Since PEG 400 is a liquid, it has a wide compatibility with various solutions, is a good solvent and thickener, and is widely used in liquid preparations, such as oral liquids. When vegetable oil is not suitable as an active ingredient carrier, PEG is the preferred material. This is mainly because PEG is stable and not easy to deteriorate. In addition, it can be mixed with high molecular weight (PEG) and the mixture has good solubility and good compatibility. PEG 4000, PEG 6000, and PEG 8000 are used for tablets, capsules, film coatings, pills, suppositories, etc. Due to the plasticity of PEG and its ability to improve the drug release of tablets during tablet making, high molecular weight PEG (PEG 4000, PEG 6000, PEG 8000) is very useful as an adhesive for tablet manufacturing. PEG can make the surface of the tablet shiny and smooth, and not easily damaged. A small amount of high molecular weight PEG (PEG 4000, PEG 6000, PEG 8000) can prevent sugar-coated tablets from sticking to each other and to the bottle. In addition, PEG can also be used as an osmotic laxative. The commonly used powder with a molecular weight of 3350 is 17g dissolved in water and taken orally daily to treat constipation.

* PEG raw material list:

Polyethylene Glycol 3350

Polyethylene Glycol 3350 (PEG 3350) is a multifunctional polymer compound widely used in medicine, industry and daily life. PEG 3350 is composed of repeating units of ethylene glycol (C2H4O) and has a molecular weight of about 3350, which gives it unique physical and chemical properties. In the medical field, PEG 3350 is often used to treat constipation. As an osmotic laxative, it absorbs water in the intestine, softens the stool and increases its volume, thereby promoting defecation. Another notable feature of PEG 3350 is that it has a mild effect and usually does not cause abdominal pain or sharp laxative reactions. Therefore, it is widely used in the daily treatment of the elderly and patients with chronic constipation. In industry, PEG 3350 is often used in the production of cosmetics, lubricants and pharmaceutical excipients due to its good wettability and low toxicity. It is also a common excipient and solvent in the pharmaceutical industry to enhance the solubility and stability of drugs. In addition, PEG 3350 is also used for protein crystallization and DNA preparation in biochemistry and molecular biology research.