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Polyethylene Glycol 400, recognized as PEG 400, works as a low-molecular-weight polymer from ethylene oxide and water. People in the pharmaceutical world depend on this material, especially for injection purposes, because of its high stability, low toxicity, and compatibility with a range of drugs. Its chemical makeup allows it to dissolve in water and many organic solvents, leading to a range of uses. The molecular formula, C2nH4n+2On+1, shows how the repeating ethylene oxide units build up the molecule, and the average molecular weight hovers around 380–420 g/mol. As a pharma grade product, PEG 400 stands out with strict control over heavy metals, water content, and purity so it meets the standards set by British Pharmacopoeia (BP), European Pharmacopoeia (EP), and United States Pharmacopeia (USP).
Polyethylene Glycol 400 usually appears as a clear, colorless, and nearly odorless liquid at room temperature. Its viscosity splits the difference between water and heavier grades of PEG, which makes it manageable to handle in manufacturing settings. Density clocks in at about 1.125 g/cm³ at 20°C, a detail that matters when measuring for precise pharmaceutical processes. PEG 400 resists freezing and stays stable across a range of conditions, does not crystallize at temperatures found in most manufacturing or medical environments, and rarely degrades when exposed to light or ordinary temperatures. It can exist in liquid, flake, powder, and sometimes pearl forms, but pharmaceutical injection grades always stick to the liquid form for consistency and safety.
The backbone of PEG 400 consists of repeating oxygen-carbon bonds. Each molecule lines up as a linear chain without cross-linking, meaning it flows rather than forming a bulky solid. The presence of terminal hydroxyl groups gives it a chemical edge, making PEG 400 a good solvent and an effective carrier for various active pharmaceutical ingredients. Compatibility with salts, acids, and bases helps broaden its role in formulation science. Purity stays high to remove the risks attached to potential contaminants, especially in injectable drugs. Chemical analysis by nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy confirms absence of impurities and consistent structure batch-to-batch.
PEG 400 offered for pharma injection meets strict purity, color, and microbiological standards. Water content rarely climbs above 1%, and levels of ethylene glycol, diethylene glycol, and other impurities stay tightly regulated, usually far below 0.2%. Packages ship under the Harmonized System (HS) Code 29053990—this helps customs identify its chemical composition and intended pharmaceutical use. Specifications cover appearance (clear, colorless liquid), density (1.125 g/ml), pH (4.5–7.5 for a 5% solution), average molecular weight, and limits for residue on ignition and heavy metals, all vital for safety and consistency.
People handling PEG 400 for injection work with a substance that offers a strong safety profile. Toxicity stays low, and the compound rarely triggers reactions in patients. Still, excessive exposure—especially as a raw material in industrial settings—can lead to slight irritation of the eyes, skin, or respiratory tract. It does not act as a hazardous substance under most global regulatory systems; material safety data sheets suggest gloves and goggles during handling, as basic precautions. No classification as carcinogenic, mutagenic, or reprotoxic emerges from current studies. PEG 400 is not considered harmful at the levels used for injection, though any substance can prompt problems with grossly excessive exposure or misuse.
Producing high-grade injectable drugs often calls for a carrier with tight performance and safety margins. PEG 400 fits this bill because it dissolves both hydrophilic and lipophilic drugs, supports drug stability, and keeps solubility under control during manufacturing and injection. In my experience developing and reviewing pharmaceutical formulations, switching between molecular weights (200, 400, 600) changes viscosity and solubility properties, but the 400 grade almost always finds its way into parenteral formulations where those balance points matter most. Companies also monitor for diethylene glycol contamination, since this presents an acute toxicity risk and led to historical tragedies in drug safety.
Consistency and traceability stay central to meeting international regulations. Producers test each batch stringently for molecular weight, heavy metals, pH, water, and other potential contaminants. Regulatory auditors demand transparent supply chains and regular third-party audits. Drug manufacturers face ongoing challenges to exclude impurities below thresholds and carry out routine re-validation of supply sources. Labs update test protocols whenever global pharmacopoeia standards shift. Such diligence is necessary because injectable drugs carry greater consequences for failure—any lapse can lead to recalls, lawsuits, or loss of product registrations in major markets.
PEG 400 does not persist in the environment. Microorganisms readily break it down into smaller, harmless compounds. This gives some peace of mind that accidental leaks or spills should not accumulate or cause long-term harm outside concentrated industrial settings. Wastewater rules usually allow PEG at low concentrations, though local regulations can vary. Proper, responsible handling—avoiding discharge in bulk, sticking to controlled waste streams—still makes sense if you want to steer clear of headaches with local environmental agencies.
Chengguan District, Lanzhou, Gansu, China
