Polyethylene Glycol for Eye Drops

As a high molecular compound, polyethylene glycol (PEG) is widely used in daily life and medicine. Its excellent performance and multifunctional characteristics make it play an irreplaceable role in various occasions. For example, polyethylene glycol is often used in eye care products such as eye drops. Its excellent moisturizing and mild properties can effectively relieve dry eyes, fatigue and other discomfort symptoms and protect eye health.

Eye Drops

Eye drops are liquid medicines used for eye treatment and care. They are used to treat or relieve eye symptoms by directly dropping a certain amount of medicine into the eyes. Eye drops are widely used in medicine and daily life and are one of the commonly used preparations in ophthalmology. The main ingredients of eye drops usually include active pharmaceutical ingredients, solvents, moisturizers and preservatives. Different types of eye drops contain different ingredients according to their uses and treatment goals. Common types of eye drops include lubricant eye drops, antibacterial eye drops, antiviral eye drops, anti-inflammatory eye drops, anti-allergic eye drops, artificial tears and eye drops for the treatment of glaucoma. Among them, lubricant eye drops are mainly used to relieve dry eyes, burning sensation and foreign body sensation. This type of eye drops usually contains lubricating ingredients, such as polyethylene glycol. Polyethylene glycol is a viscosity regulator that can form a protective film on the surface of the eye, thereby increasing the wetness of the eye surface, reducing tear evaporation, and relieving dry eye symptoms.

Fig. 1. PEG for eye drops.

What are Polyethylene Glycol?

Polyethylene glycol is a widely used polymer compound formed by repeated polymerization of ethylene glycol units. Depending on the molecular weight, PEG can exhibit physical states ranging from liquid to solid. Low molecular weight PEG is generally liquid, while high molecular weight PEG is a waxy solid. This substance has many remarkable properties, including high solubility, low toxicity, biocompatibility and good lubricity, and is therefore widely used in medicine, cosmetics, industry and food. In the pharmaceutical field, polyethylene glycol is often used as a drug carrier and excipient due to its excellent biocompatibility and good solubility, including in eye drops.

* List of common polyethylene glycol used in eye drops:

As a lubricant, polyethylene glycol can effectively mimic the function of natural tears and relieve dry eyes. Dry eye is a common ophthalmic problem, mainly caused by insufficient tear secretion or excessive tear evaporation. Eye drops containing PEG can form a protective film on the surface of the eye, reduce tear evaporation, provide a long-lasting lubricating effect, and thus relieve dry eye symptoms. PEG has good adhesion and ductility, and can form a uniform and stable drug delivery system on the surface of the eye, improving the bioavailability of drugs. Adding PEG can prevent the eye drops from being quickly diluted and discharged by tears after being dropped into the eye, which allows the drug to stay on the surface of the eye for a longer time and exert a better therapeutic effect. In addition, the safety and low allergenicity of PEG are also important reasons for its widespread use in eye drops. As a widely verified biomaterial, its use can reduce irritation to the eye and is suitable for long-term or frequent use of ophthalmic drug preparations.

Polyethylene Glycol Eye Drops

The main ingredients of peg eye drops are polyethylene glycol, propylene glycol and hydroxypropyl guar gum (HP-Guar, hydroxypropyl mannose polymer gel), etc., which are designed to provide patients with good ocular surface protection and lubrication, promote the repair of damaged corneal areas caused by dry eyes, and provide lasting relief of dry eye symptoms. They are especially suitable for water-deficient and mucin-deficient dry eyes. Mechanistically, HP-Guar is a type of water-soluble natural polysaccharide, which is used to increase the viscosity of eye drops, ensure that it can be spread quickly and evenly when entering the eye, improve the comfort of eye drops, and better balance the viscosity and comfort of artificial tears. After entering the eye, with the dilution of sorbitol, HP-Guar cross-links with borate to form a mesh gel structure, allowing the active lubricant polyethylene glycol to stay on the ocular surface for a long time, prolong the tear film breakup time, and provide lasting relief of dry eye symptoms. Generally, polyethylene glycol eye drops can be used in the following special situations:

• Assisting long-term use of contact lenses: Long-term wear of contact lenses is often easily accompanied by eye irritation symptoms, including dryness, discomfort, soreness, and eye fatigue. Among contact lens wearers, 25% to 50% suffer from contact lens-related dry eyes. Several studies have shown that polyethylene glycol eye drops can stabilize the ocular surface environment and provide long-term relief of dry eye symptoms associated with contact lens use.
• Protecting cataract perioperatively: In a prospective, parallel, randomized, double-blind, single-center clinical study, Davidson et al. evaluated the efficacy of polyethylene glycol eye drops in patients with occasional ocular irritation symptoms or a history of dry eyes associated with environmental factors during routine cataract extraction. The results showed that the combination of polyethylene glycol eye drops with standard care can provide better ocular surface protection, significantly improve ocular surface comfort, and reduce the signs and symptoms of dry eyes.
• Application under adverse environmental conditions: Adverse environmental conditions can aggravate the signs and symptoms of dry eyes. Differences in temperature and humidity may affect the effectiveness of artificial tears in relieving dry eye symptoms. Several studies have confirmed that polyethylene glycol eye drops can achieve stable therapeutic effects under different temperature and humidity conditions.

Is Polyethylene Glycol Safe in Eye Drops?

Davitt et al. reported a prospective, randomized, controlled, multicenter, double-blind study involving 113 dry eye patients. The results showed that the use of polyethylene glycol eye drops can reduce corneal and conjunctival staining as early as one week, and the average corneal staining is significantly reduced at two weeks (P=0.0009), and the average conjunctival staining is significantly reduced at four weeks (P=0.0475). In addition, the average scores of patients' ocular symptoms and ocular surface disease index (OSDI) were significantly reduced compared with baseline, and the tolerance was good. Fernandez et al. confirmed that 30 days of treatment with polyethylene glycol eye drops (containing propylene glycol) can significantly reduce the expression of inflammatory factors HLA-DR (P=0.02), improve corneal staining (P=0.01), OSDI score (P= 0.02) and tear film breakup time (TBUT; P= 0.01), indicating that ocular surface inflammation is reduced, thereby improving the signs and symptoms of dry eyes. Many studies have confirmed that the use of polyethylene glycol eye drops (all containing propylene glycol) to treat dry eyes is convenient, effective, and has good patient acceptance and tolerance.

Polyethylene Glycol Eye Drops vs. Sodium Carboxymethylcellulose Eye Drops

Multiple studies have shown that polyethylene glycol eye drops and sodium carboxymethylcellulose eye drops are similar in improving ocular surface health, relieving signs and symptoms of dry eye, and patient-reported treatment effect scores. Davitt et al. found that patients treated with polyethylene glycol eye drops had a more significant reduction in corneal and conjunctival staining than those treated with sodium carboxymethylcellulose eye drops. In 2012, Waduthantri et al. compared the efficacy of another type of sodium carboxymethylcellulose eye drops with polyethylene glycol eye drops in Chinese dry eye patients. The results showed that there was no significant difference between the two drugs in improving symptoms and changing objective signs of dry eye (such as corneal fluorescein staining, TBUT, and Schirmer test results).

Polyethylene Glycol Eye Drops vs. Hydroxypropyl Methylcellulose Eye Drops

Maharana et al. conducted a retrospective analysis of patients with dry eye and showed that there were no significant differences in OSDI, TBUT, and Schirmer's assessments between patients using hydropropyl methylcellulose eye drops and those using polyethylene glycol eye drops.

Polyethylene Glycol 400 Eye Drops

Polyethylene Glycol 400 (PEG 400) is an important lubricant and moisturizer, widely used in eye drops, mainly for relieving eye discomfort and dry eye syndrome. PEG 400 is a water-soluble polymer compound with good lubricity and moisturizing properties. In eye drops, it can form a uniform protective film on the surface of the eyeball, effectively reducing the friction between the eyelid and the cornea, and increasing the comfort of the eye. It has strong hygroscopicity and can absorb and retain water, thereby maintaining the moist state of the surface of the eyeball. In addition, as one of the ingredients of eye drops, PEG 400 has good biocompatibility and safety. Clinical studies have shown that it is not easy to cause eye irritation, let alone toxic effects on the cornea and conjunctiva. In addition, PEG 400 can also work together with other active ingredients in eye drops to enhance the effect of the drug. For example, it can be used in combination with sodium hyaluronic acid, propylene glycol, etc. to further improve the lubrication effect and stability of eye drops, thereby providing more comprehensive eye protection.

* List of polyethylene glycol derivatives: