Hydroxypropyl Methylcellulose

Hydroxypropyl methylcellulose (HPMC), also known by its INN name hypromellose, is a semi-synthetic, non-ionic cellulose ether prepared by treating purified cellulose with methyl chloride and propylene oxide. The resulting polymer combines hydrophilic and hydrophobic character in a tuneable ratio, making it the single most widely used excipient polymer in oral dosage form design.

In tablet manufacturing, low-viscosity HPMC grades (E5, E6, E15) serve as the primary polymers in aqueous film coating systems, forming smooth, clear films that protect the tablet core, mask taste and improve patient compliance. Higher-viscosity grades (K4M, K15M, K100M) are the standard matrix formers for hydrophilic controlled-release tablets: the polymer swells on contact with gastrointestinal fluid, forming a gel layer that controls drug diffusion and erosion over 8 to 24 hours.

Beyond solid dosage forms, HPMC is used as a demulcent in artificial tear solutions, as the shell material for vegetarian hard capsules (replacing gelatin), as a binder in wet granulation, and as a viscosity modifier in topical and ophthalmic formulations. Its food-grade variant (E464) functions as a thickener and emulsifier, while construction-grade HPMC is added to tile adhesives and cement renders for water retention.

HPMC is classified by substitution type — E (2910), K (2208) and F (2906) — which determines the ratio of methoxyl to hydroxypropoxyl groups, and by viscosity grade, denoted by the number following the letter (e.g. E5 = 5 mPa·s nominal viscosity of a 2 % aqueous solution at 20 °C). Chelora supplies all major types and grades to IP, BP and USP-NF specifications.