Poloxamer

• BPPoloxamers
• Ph. Eur.Poloxamers
• USP–NFPoloxamer

Kolliphor P 188; Kolliphor P 407; Lutrol F 68; Lutrol F 127; Pluronic F68; Pluronic F127; poloxamera; polyethylene–polypropylene glycol; Synperonic PE

α-Hydro-ω-hydroxypoly(oxyethylene)a poly(oxypropylene)b poly(oxyethylene)a block copolymer · [9003-11-6]

HO(C2H4O)a(C3H6O)b(C2H4O)aH · ≈ 2 000–17 500 depending on type (poloxamer 188 ≈ 7 700–9 500; poloxamer 407 ≈ 9 800–14 600)

Surfactant, emulsifier, Gelling agent, viscosity modifier, Solubilising agent

Typical concentrations: 15–50% gelling · Dosage forms: Liquid, Semi-solid, Sterile (parenteral/ophthalmic)

Nonionic surfactants used as emulsifiers, solubilisers, wetting agents and stabilisers in oral, parenteral and topical products; poloxamer 188 is used in intravenous fat emulsions and as a stabiliser and shear protectant in cell culture and protein products. Concentrated aqueous solutions of poloxamer 407 (typically about 15–30% w/w) form thermoreversible gels that are liquid when cold and set at body temperature. Typical levels: wetting agent 0.01–5%; stabilising agent 1–5%; tablet excipient or coating 5–10%; gelling agent 15–50%.

Synthetic block copolymers of ethylene oxide and propylene oxide, with a central hydrophobic polyoxypropylene block flanked by two hydrophilic polyoxyethylene blocks. The three-digit number identifies the type: the first two digits multiplied by 100 give the approximate molecular weight of the polyoxypropylene block, and the last digit multiplied by 10 gives the approximate percentage of polyoxyethylene. They are white or almost white and nearly odourless and tasteless.

Physical form

poloxamer 124 is a liquid; poloxamers 188, 237, 338 and 407 are white, waxy, free-flowing prills or cast solids

Melting point

about 52 °C (poloxamer 188); about 56 °C (poloxamer 407)

HLB

about 29 (poloxamer 188); about 22 (poloxamer 407)

pH

5.0–7.5 (2.5% w/v aqueous solution)

Solubility

solid grades freely soluble in water and ethanol; practically insoluble in ether, liquid paraffin and fixed oils

Stable materials. Aqueous solutions are stable in the presence of acids, alkalis and metal ions, but they support mould growth and should be preserved if stored. Store in a well-closed container in a cool, dry place; some grades contain an antioxidant such as butylated hydroxytoluene.

Depending on the relative concentrations, poloxamer 188 is incompatible with phenols and parabens. Poloxamers can reduce the activity of some preservatives by micellar solubilisation.

Made by polymerising propylene oxide onto propylene glycol to form the central polyoxypropylene block, then adding ethylene oxide to both ends of the chain, using an alkaline catalyst that is subsequently neutralised and removed.

Poloxamers are generally regarded as non-toxic and non-irritant, and they are not metabolised in the body. They are used in oral, topical and parenteral products, including intravenous use of poloxamer 188.

Observe normal precautions for the quantity handled. Eye protection and gloves are recommended, and a dust mask when handling powdered grades.

Included in the FDA Inactive Ingredient Database (IV injections; inhalation; oral powders, solutions, suspensions and syrups; ophthalmic and topical preparations) and in parenteral and non-parenteral medicines licensed in Europe.

Polyethylene glycol; polyoxyethylene alkyl ethers; polysorbates.

The pharmacopoeias cover poloxamers 124, 188, 237, 338 and 407. Thermoreversible poloxamer 407 gels are best prepared by the 'cold method', dissolving the polymer in chilled water; the gelation temperature falls as the polymer concentration increases and is shifted by salts and other additives.