Hypromellose phthalate

• BPHypromellose Phthalate
• JPHypromellose Phthalate
• Ph. Eur.Hypromellose Phthalate
• USP–NFHypromellose Phthalate

HP-50; HP-55; HP-55S; HPMCP; hydroxypropyl methylcellulose phthalate; hypromellosi phthalas

Cellulose, hydrogen 1,2-benzenedicarboxylate, 2-hydroxypropyl methyl ether · [9050-31-1]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Coating agent, film former

Typical concentrations: — · Dosage forms: Solid

Used mainly as an enteric film coating for tablets, granules and capsules, applied from organic solvent solutions (typically about 5–10% w/w polymer) or from aqueous dispersions with a plasticiser. It is also used as a carrier in solid dispersions to improve the dissolution of poorly soluble drugs, and in sustained-release matrices and microparticles.

White to slightly off-white, odourless or nearly odourless, tasteless flakes or granular powder. Pharmacopoeias define two substitution types: 200731 (HP-50) and 220824 (HP-55), which differ in phthalyl (carboxybenzoyl) content and therefore in the pH at which they dissolve.

Dissolution pH

HP-50 ≥ 5.0; HP-55 ≥ 5.5

Carboxybenzoyl content

21–27% (type 200731); 27–35% (type 220824)

Solubility

practically insoluble in water, dilute acids and ethanol; soluble in acetone–methanol, acetone–ethanol and methanol–dichloromethane mixtures and in aqueous alkali

Film properties

forms flexible films with less plasticiser than cellulose acetate phthalate

Chemically and physically stable for several years at room temperature. Under high temperature and humidity it slowly hydrolyses, releasing phthalic acid, although it is less susceptible than cellulose acetate phthalate. Store in a well-closed container in a cool, dry place.

Incompatible with strong oxidising agents. Its free carboxyl groups can react with basic drugs and alkaline excipients; splitting of enteric films has been reported when coatings contain high levels of some fillers such as talc.

Prepared by esterifying hypromellose with phthalic anhydride in acetic acid, using anhydrous sodium acetate as catalyst. The product is precipitated in water, washed and dried.

Used in oral products and regarded as non-toxic and non-irritant; it is not absorbed from the gastrointestinal tract.

Observe normal precautions for the quantity handled; eye protection and gloves are recommended. When organic solvent coating solutions are used, the precautions appropriate to the solvents apply.

Included in the FDA Inactive Ingredient Database (oral capsules and tablets) and in non-parenteral medicines licensed in Europe.

Cellulose acetate phthalate; hypromellose; hypromellose acetate succinate; polyvinyl acetate phthalate.

HP-55 is the common choice for conventional enteric coating, while HP-50 dissolves at a slightly lower pH and is used when earlier release in the duodenum is wanted. Adequate coat thickness is essential to resist gastric fluid, and coated products should be tested by a two-stage (acid then buffer) dissolution test.