Description
A pH-sensitive cellulose ester based on the Hypromellose backbone rather than the cellulose acetate backbone of CAP. Used as an enteric coating polymer with selectable threshold pH (HP-50 dissolving above approximately pH 5.0, HP-55 above approximately pH 5.5), giving formulators control over the small-intestinal segment of release.
White to off-white free-flowing powder or granules. Soluble in acetone, methanol-methylene chloride blends, and dilute aqueous alkali above the threshold pH. Insoluble in water below threshold pH and in most aliphatic hydrocarbons.
We supply pharmaceutical-grade Hypromellose Phthalate from manufacturers in China holding ISO, GMP, USP/EP/JP DMF, Halal, Kosher, and other certifications relevant to the product and production.
Common market grades include HP-50 (phthalyl content 21 to 27 percent, threshold pH approximately 5.0, used for duodenal release) and HP-55 (phthalyl content 27 to 35 percent, threshold pH approximately 5.5, used for upper small-intestinal release). HP-55S is a higher-viscosity variant for spray-applied enteric coatings.
Bulk and reduced-MOQ shipments. Batch-level COA covering identification, methoxy and hydroxypropoxy content, phthalyl content, free acid, viscosity, loss on drying, residue on ignition, heavy metals, residual solvents, and microbiology against USP, EP, JP, and BP monographs.
Introduction
Hypromellose Phthalate was developed in the 1970s as a Hypromellose-backbone alternative to Cellulose Acetate Phthalate, offering selectable threshold pH and improved film flexibility. It is now one of the standard enteric coating polymers in regulated pharmaceutical markets alongside CAP, Hypromellose Acetate Succinate, and the methacrylate Eudragit L and S grades.
Production starts from pharmaceutical-grade Hypromellose that is reacted with phthalic anhydride in glacial acetic acid under controlled conditions. The substitution ratio of methoxy, hydroxypropoxy, and phthalyl groups defines the grade (HP-50 versus HP-55) and the corresponding threshold pH.
Listed in USP-NF, EP, JP, and BP monographs. FDA Inactive Ingredient Database listed for oral solid dosage forms.
The enteric dissolution mechanism is ionization of the phthalic acid carboxyl groups, with the threshold pH tunable by the phthalyl-to-hypromellose ratio. HP-50 dissolves above approximately pH 5.0 (duodenal release), HP-55 above approximately pH 5.5 (jejunal release), giving formulators direct control over the small-intestinal segment of release.
Strategic position: the standard enteric polymer for proton pump inhibitor pellets, enzyme capsules, and probiotic capsules where the pH threshold and film flexibility are both formulation-critical.
Where it is used
- Enteric film coating on acid-labile tablets and capsules
- Selectable threshold pH enteric coating (HP-50, HP-55)
- Enteric coating on proton pump inhibitor tablets and pellets
- Enteric coating on enzyme and probiotic capsules
- Multiparticulate pellet coating in capsule fills
- Matrix former in pH-triggered controlled-release systems
- Polymer carrier in amorphous solid dispersions for solubility enhancement
- Enteric coating on nutraceutical and OTC delayed-release products
Technical data
| Item | Specification |
|---|---|
| Appearance | White to off-white free-flowing powder or granules |
| Compliance | USP/NF, EP, JP, BP current edition |
| Identification | Conforms to pharmacopoeial tests |
| Methoxy content (dried basis) | 18.0% to 24.0% (HP-50, HP-55) |
| Hydroxypropoxy content (dried basis) | 5.0% to 10.0% |
| Phthalyl content (HP-50) | 21.0% to 27.0% |
| Phthalyl content (HP-55) | 27.0% to 35.0% |
| Free acid (as phthalic acid) | ≤ 1.0% |
| Viscosity (10% solution, 20 °C) | Grade dependent |
| Loss on drying | ≤ 5.0% |
| Residue on ignition | ≤ 0.2% |
| Heavy metals (as Pb) | ≤ 10 mg/kg |
| Residual solvents | Conforms to ICH Q3C limits |
| Enteric solubility threshold | pH ≥ 5.0 (HP-50) or ≥ 5.5 (HP-55) |
| Particle size | Per grade specification |
| Total aerobic count | ≤ 1,000 CFU/g |
| Yeast and mould | ≤ 100 CFU/g |
| E. coli, Salmonella | Absent |
| Source | Purified wood pulp cellulose |
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