What Is Polyoxyethylene (35) Castor Oil BP EP USP Pharma Grade?

Introduction to Polyoxyethylene (35) Castor Oil

Polyoxyethylene (35) Castor Oil, also known as PEG 35 Castor Oil or Cremophor EL, is a nonionic surfactant produced by reacting castor oil with ethylene oxide. This grade meets the standards of BP, EP, and USP pharmacopoeias, which means it stands up to some of the strictest requirements for use in pharmaceutical applications. The manufacturing process involves adding about 35 units of ethylene oxide to each molecule of castor oil, which transforms its physical nature and opens up a range of new uses. In my experience with pharma excipients, this ingredient’s unique structure gives it properties that drug formulators look for, especially when you need something that keeps a solution clear, stable, and able to mix oil and water.

Chemical Properties and Molecular Structure

Chemically, Polyoxyethylene (35) Castor Oil carries the formula C₅₇H₁₀₄O₂₁. Each molecule consists of a castor oil core surrounded by 35 ethylene oxide units. That much ethoxylation changes the native oil into a much more hydrophilic material. Talking strictly about structure, this creates a long chain with both lipophilic and hydrophilic segments, making it very effective for solubilizing oily ingredients in water. The density of the product falls in the range of 1.06 to 1.10 g/cm³ at 20°C, typical for polyethylene glycol derivatives, which gives it enough heft without making processing a challenge. Most forms used in pharmaceuticals are clear, viscous liquids, though some variants come as pastes or semi-solids, especially if stored at lower temperatures. As a liquid, it flows smoothly at room temperature, but it thickens up in cooler conditions—sometimes showing waxy or pearly flakes if chilled.

Physical Forms and Specifications

This grade of castor oil polyoxyethylene comes mainly as a pale yellow to amber, clear to slightly opalescent liquid. Depending on storage, it may develop crystalline flakes that dissolve when warmed slightly. Most pharma-grade suppliers specify a minimum polyethylene glycol content of 80%, an acid value below 2, and a saponification value in the range of 50 to 60. Water content often sits below 2% to keep the product stable. As for the hazardous profile, Polyoxyethylene (35) Castor Oil finds a safe spot in most pharmaceutical settings, though it’s important for users to monitor for possible hypersensitivity reactions in some patients. Chemical safety assessments often mark it as a low-to-moderate hazard. Direct contact with eyes or skin shouldn’t cause severe irritation, but personnel should follow good manufacturing practices and use gloves and goggles.

Function and Application in Pharmacy

Formulators often reach for Polyoxyethylene (35) Castor Oil to solubilize lipophilic or poorly water-soluble drugs. Its surfactant properties make it extremely valuable in injectable drugs, oral liquids, and topical solutions. As someone who has watched the development of injectable cancer therapies, I’ve seen countless formulations succeed or fail based on the right excipient. Polyoxyethylene (35) Castor Oil helps clear up cloudy solutions and lets oily actives play nice with hydrophilic environments. It works by forming micelles—tiny bubbles that trap oil-soluble molecules—allowing them to dissolve in water. The material’s ability to handle a range of pH values, stay stable during sterilization, and avoid breaking down under normal storage conditions makes it almost a go-to for certain drug formulations. Its pharmaceutical-grade purity means there’s a strict limit on toxic impurities like ethylene oxide and dioxane.

HS Code, Raw Materials, and Regulatory Details

As for trade and customs, Polyoxyethylene (35) Castor Oil generally appears under HS Code 34021300, which covers nonionic organic surface-active agents. Producers start with castor oil pressed from the seeds of Ricinus communis and use industrial-grade ethylene oxide, a feedstock derived from the petrochemical industry. For every kilogram produced, the environmental impact reflects both the farming of castor beans and the synthetic process to graft those 35 units of ethylene oxide onto each triglyceride molecule. Pharmaceutical grades must meet not only chemical purity norms but also microbiological safety and low endotoxin levels. Regulatory authorities enforce documentation from raw material origin all the way to final lot testing. All this oversight means that pharmaceutical companies and their customers get predictable performance batch to batch—a far cry from unregulated chemicals that shift from drum to drum.

Risks, Hazards, and Safety

Safety remains a factor, as with any chemical. The primary gripe with Polyoxyethylene (35) Castor Oil comes from rare but serious allergic reactions, especially during intravenous use. Incidents like anaphylaxis underline the need for continued research into safer excipients or ways to remove problematic byproducts. People with a background in hospital pharmacy often recognize the trade-offs—sometimes the benefits outweigh the small but real risks for critical drugs that have no better alternative. On a practical level, workers handling large amounts wear gloves and safety glasses and use well-ventilated spaces to avoid long exposures or spills. Material Safety Data Sheets call out the importance of preventing environmental release, since residues in waterways can affect aquatic organisms due to surfactant action.

Potential Solutions and Improvements

One road forward for minimizing issues involves better purification steps, especially to get rid of unwanted residuals from ethoxylation. Alternative surfactants based on natural materials, like polyglyceryl esters, offer promise for similar performance with different risk profiles. Research groups and excipient manufacturers are working on greener production and tighter controls on impurities. Since regulations keep evolving, industry works hand in hand with regulators to update specs, ensuring that what goes into medicine cabinets passes every modern safety and environmental standard. If formulators keep skeptical, open eyes, and manufacturers put resources into transparency and safety improvements, Polyoxyethylene (35) Castor Oil will keep playing an important role in how essential drugs reach patients.