Hyprolose

Hyprolose (Hydroxypropyl Cellulose): A Comprehensive Reference

1. Identity and Nomenclature

Hyprolose is the International Nonproprietary Name (INN) and official pharmacopeial designation for hydroxypropyl cellulose (HPC). Hyprolose is an ether of cellulose where some of the hydroxyl groups of the cellulose have been hydroxypropylated, forming -OCH₂CH(OH)CH₃ groups. Hydroxypropyl cellulose (cellulose, 2-hydroxypropyl ether) is a derivative of cellulose with both water solubility and organic solubility.

It is important to note that hyprolose (HPC) and hypromellose are distinct but related compounds. Hypromellose and hydroxypropyl cellulose are not the same. Hypromellose, also known as hydroxypropyl methylcellulose (HPMC), is a semi-synthetic, inert, viscoelastic polymer used as an ophthalmic lubricant, an oral excipient, a tablet binder, and a film former. Hypromellose is a derivative of cellulose that contains hydroxypropyl groups, while hydroxypropyl cellulose is a polymer of cellulose that contains hydroxypropyl groups. The key chemical distinction is that HPMC contains both methyl and hydroxypropyl substituents, while HPC (hyprolose) contains only hydroxypropyl substituents.

1.1 Synonyms and Official Names

• Hyprolosum (Latin); Hydroxypropyl cellulose (German); Hyprolose (French); Hiprolosa (Spanish); Hydroxypropylcellulose (DCF, JAN); E 463 (International food additive number).
• The USP/NF CAS registry number is 9004-64-2, and the compound is formally defined as a partially substituted poly(hydroxypropyl) ether of cellulose.
• It has two primary grades: HPC and L-HPC, the latter being the low-substituted form which functions as a binder and disintegrant in the pharmaceutical field. The European food additive numbers for these are E463 and E463a, respectively.

1.2 Chemical Structure

HPC is a semi-synthetic polymer derived from cellulose, a natural polymer composed of repeating D-glucose units linked by β(1→4) glycosidic bonds. It is an ether of cellulose in which hydroxypropyl groups (–CH₂CHOHCH₃) are attached to the hydroxyls present in the anhydroglucose rings of cellulose by ether linkages. The molecular weight of HPC used in pharmaceutical ophthalmic applications is typically 1 × 10⁶.

HPC can be divided into two grades, HPC (regular) and L-HPC (low-substituted hydroxypropyl cellulose), depending on the degree of substitution or the amount of hydroxypropoxy groups in the cellulose backbone. As HPC has a larger number of hydroxypropoxy groups than L-HPC, this makes HPC soluble in water while L-HPC is not. Hydroxypropyl cellulose has a combination of hydrophilic and hydrophobic groups, so its lower critical dissolution temperature (LCST) is 45°C. HPC is very soluble in water below 38°C, forming a clear colloidal solution. In hot water, it is insoluble and precipitates as swollen flakes at a temperature between 40 and 45°C.

1.3 Physical Properties

Hydroxypropyl cellulose is an off-white, odorless, tasteless powder. It is soluble in water below 38°C, and in many polar organic solvents such as ethanol, propylene glycol, dioxane, methanol, isopropyl alcohol (95%), dimethyl sulfoxide, and dimethyl formamide. With CAS number 9004-64-2, HPC exists as a white to off-white powder or granules and is soluble in cold water, making it useful for various food applications.

1.4 Natural Source and Manufacturing

HPC is cellulose obtained directly from strains of fibrous plant material and partially etherified with hydroxypropyl groups. It is a low-substituted poly(hydroxypropyl) ether of cellulose, manufactured by partial etherification of the anhydroglucose units of pure cellulose (wood pulp) with propylene oxide/hydroxypropyl groups. A purified form of cellulose is reacted with sodium hydroxide to produce a swollen alkali cellulose that is chemically more reactive than untreated cellulose. The alkali cellulose is then reacted with propylene oxide at elevated temperature and pressure. The propylene oxide can be substituted on the cellulose through an ether linkage at the three reactive hydroxyls present on each anhydroglucose monomer unit of the cellulose chain. Etherification takes place in such a way that hydroxypropyl substituent groups contain almost entirely secondary hydroxyls.

2. Traditional and Historical Context

Hyprolose as a chemically defined semi-synthetic compound has no pre-modern history of traditional use; it is a product of 20th-century industrial chemistry. However, its precursor — plant-derived cellulose — has deep roots in historical practice. While HPC is primarily known today as a pharmaceutical excipient and a food additive, its roots in traditional remedies can be traced back to the use of plant-derived gums and cellulose for soothing and protective applications. In earlier times, natural cellulose extracts were employed in folk medicine for their demulcent properties, providing relief for irritated mucous membranes and acting as gentle bulk-forming agents for digestive health.

Over the decades, modern hypromellose and HPC emerged as refined, standardized versions of these traditional cellulose-based remedies. The cellulose polymer itself — found in all plant cell walls — has been consumed by humans throughout history as dietary fiber. The deliberate semi-synthetic modification into hydroxypropyl cellulose was developed in the mid-20th century to serve pharmaceutical and food technology needs. Hydroxypropyl cellulose has been used in food production for decades with minimal documented safety concerns.

3. Key Chemical Constituents and Pharmacopeial Standards

Hyprolose itself is the single active constituent in its pharmaceutical applications, functioning by virtue of its physicochemical properties rather than containing discrete bioactive small molecules. Its pharmaceutical characterization is governed by official monographs in multiple pharmacopeias.

The Hydroxypropyl Cellulose monograph has been officially approved and incorporated into USP–NF. Having reached Stage 6 of the PDG (Pharmacopeial Discussion Group) process, the Hydroxypropyl Cellulose monograph has been formally approved by the USP Monographs—Excipients Expert Committee. Key specification changes defined the compound as "partly O-(2-hydroxypropylated) cellulose" and established that it must contain not less than 53.4% and not more than 80.5% of hydroxypropoxy groups, calculated on the dried basis, verified by a GC capillary assay.

Multiple viscosity grades of HPC exist based on molecular weight, reflecting differences in pharmaceutical functionality. Grades include HPC-SSL (viscosity in 2% aqueous solution at 20°C: 2.0–2.9 mPa·S), HPC-SL (3.0–5.9 mPa·S), HPC-L (6.0–10.0 mPa·S), HPC-M (150–400 mPa·S), and HPC-H (1,000–4,000 mPa·S).

4. Mechanisms of Action

Hyprolose does not function through receptor binding, enzyme inhibition, or classical pharmacological pathways. Its effects are primarily physical and physicochemical.

4.1 Ophthalmic Mechanism

Hydroxypropyl cellulose acts as an ophthalmic demulcent and lubricant. Its mechanism is purely physical rather than pharmacological in the sense of receptor binding or metabolic alteration. Upon placement in the inferior cul-de-sac (the space between the lower eyelid and the eyeball), the insert absorbs fluid from the patient's available tears, causing the insert to swell and become a soft, gel-like mass. Over a period of several hours (typically 6 to 8 hours or longer), the swollen insert slowly dissolves, releasing the polymer into the tear film.

Hydroxypropyl cellulose acts to stabilize and thicken the precorneal tear film and prolong the tear film breakup time, which is usually accelerated in patients with dry eye states. Hydroxypropyl cellulose acts to stabilize and thicken the precorneal tear film and prolong the tear film breakup time. Hydroxypropyl cellulose also acts to lubricate and protect the eye.

4.2 Oral/Dietary Fiber Mechanism (Relevant to HPMC/Hypromellose)

When taken orally in sufficient quantities, the closely related compound HPMC (hypromellose) acts as a viscous, soluble dietary fiber. Hydroxypropylmethylcellulose (HPMC), a viscous, soluble dietary fiber, has been shown to be efficacious for lowering total and low-density lipoprotein cholesterol (LDL-C) concentrations. Animal research suggests the mechanism involves increased intestinal viscosity: relative to dietary cellulose, all viscosity grades of HPMC resulted in significantly lower cholesterol absorption efficiency, lower plasma cholesterol concentration, and lower liver cholesteryl ester content. The logarithm of intestinal contents ex vivo viscosity was inversely correlated with dietary cholesterol absorption (r²=0.84), and dietary cholesterol absorption was positively correlated with plasma cholesterol concentration (r²=0.89). The data suggest an independent role of intestinal contents viscosity in lowering plasma cholesterol concentration and liver cholesteryl ester content by reducing cholesterol absorption efficiency.

4.3 Formulation Excipient Mechanisms

HPC enhances the mechanical properties, stability, and bioavailability of drugs, and provides flexibility in designing various drug delivery systems. As a thickener and binder, HPC can help particles bond and form during the wet granulation process of tablet production. It has strong adhesion and can adhere fine powder particles together through wet granulation to form particles with good flowability and compressibility, which are easy to form and have good compressibility during tableting.

5. Scientific Evidence by Area of Use

5.1 Ophthalmic Use: Dry Eye Syndrome (Keratoconjunctivitis Sicca)

The most extensively studied clinical application of hyprolose is its use as a sustained-release ophthalmic insert (Lacrisert®) for moderate-to-severe dry eye syndrome. This represents the only FDA-approved therapeutic application of HPC as an active pharmaceutical ingredient.

Indication and product description: Hydroxypropyl cellulose ophthalmic inserts (Lacrisert) are indicated in patients with moderate to severe dry eye syndrome (DES), including keratoconjunctivitis sicca. They are indicated especially in patients who remain symptomatic after an adequate trial of therapy with artificial tear solutions. Lacrisert is a sterile, translucent, rod-shaped, water-soluble, ophthalmic insert made of hydroxypropyl cellulose, for administration into the inferior cul-de-sac of the eye.

Specific conditions treated: It is used to treat syndromes characterized by insufficient tear production (keratoconjunctivitis sicca), recurrent corneal erosions, decreased corneal sensitivity, exposure and neuroparalytic keratitis, and as a lubricant for artificial eyes.

Key clinical study (LAC-07-01 registry study): A multicenter, 2-visit, open-label, 4-week study was conducted to determine the acceptability of hydroxypropyl cellulose ophthalmic inserts in adult patients with a history of dry eye syndrome. Five hundred twenty patients were recruited to the intent-to-treat group. Four hundred eighteen patients completed the study, including 86 contact lens wearers, 79 with cataract diagnosis, 52 with prior cataract surgery, 22 with prior laser-assisted in situ keratomileusis, and 15 with glaucoma.

Outcomes: Mean OSDI (Ocular Surface Disease Index) total scores significantly improved by more than 25% (from 41.8±22.38 at baseline to 32.9±21.97, P≤0.0215). Hydroxypropyl cellulose ophthalmic inserts significantly reduced symptoms and clinical signs of moderate to severe DES. They also significantly improved DES in patients wearing contact lenses. Patients experienced a statistically significant improvement in quality of life, as measured by the OSDI, of 21.3%.

Subpopulation data: In subsets of patients with moderate to severe DES and comorbid conditions, hydroxypropyl cellulose ophthalmic inserts improve the symptoms of DES, ability to perform activities of daily living, and quality of life. The reported benefits may be additive to those seen with patients' existing therapies.

Long-term use data: The median length of therapy with the insert was 5.3 years, and nearly 65% of patients had used it for more than 2 years. Findings suggest that the hydroxypropyl cellulose ophthalmic insert is a relatively safe, tolerable, and effective therapy. A case report described that daily use of hydroxypropyl cellulose ophthalmic inserts effectively treated autoimmune dry eye, providing symptomatic relief, and resulted in improved objective measures of disease severity across several decades. Simultaneous use of the inserts and contact lenses was well tolerated without any significant side effects or changes in visual acuity. Dry eye is a chronic disease often requiring long-term management.

Evidence strength: The evidence supporting the ophthalmic use of HPC inserts for moderate-to-severe dry eye syndrome is moderate in overall quality. Published studies are predominantly open-label, observational, or registry-based, lacking placebo-controlled randomized design. Mechanistic plausibility is well established, and FDA approval supports clinical legitimacy. The cost-effectiveness and long-term patient data for hydroxypropyl cellulose inserts await further validation.

5.2 Cardiovascular / Lipid-Lowering Effects (HPMC; Related Compound)

Clinical research on cholesterol-lowering effects has focused primarily on HPMC (hypromellose), the closely related compound, rather than hyprolose (HPC) specifically. This evidence is included here for completeness and context, as both belong to the same cellulose ether class and are sometimes discussed interchangeably in the dietary fiber literature.

Randomized controlled trial: Hydroxypropylmethylcellulose (HPMC) is a food gum having several structural and functional properties in common with hypocholesterolemic soluble fibers. The safety and cholesterol-lowering efficacy of HPMC, incorporated into a National Cholesterol Education Program Step I diet, was compared with placebo in patients with mild to moderate hypercholesterolemia. After an 8-week dietary lead-in phase, 160 patients with LDL cholesterol between 130 and 200 mg/dl and triglycerides <300 mg/dl were randomized to placebo, 2.5, 5.0, or 7.5 g/day of HPMC for a 6-week treatment period. HPMC significantly lowered total, LDL, and non–HDL cholesterol.

Multi-formulation pilot study: In a randomized, double-blind pilot study, 165 men and women with primary hypercholesterolemia consumed a control product or an HPMC-containing test bar or drink for 4 weeks. HPMC-containing products delivered 3, 5, or 10 g of HPMC of low, moderate, moderately high, or high viscosity (9 HPMC groups, each with approximately 15 subjects). All HPMC groups showed LDL-C reductions ranging from 6.1 to 13.3% (P <.05 vs. baseline for 6 of the 7 groups), compared with a nonsignificant reduction (1.9%) in the control group. Changes in total and non-high-density lipoprotein cholesterol paralleled those for LDL-C. Concentrations of HDL cholesterol, triglycerides, apolipoprotein B, and high-sensitivity C-reactive protein were not significantly altered.

Evidence strength: This pilot study provides preliminary evidence to support the efficacy of various formulations of HPMC for reducing cholesterol carried by atherogenic particles in men and women with primary hypercholesterolemia. Additional research will be required to more clearly define the roles of viscosity and dosage on the lipid-altering effects of HPMC. HPMC soluble fiber, especially high-viscosity grades, significantly lowers cholesterol at well-tolerated doses, showing promise as a treatment of hypercholesterolemia. The evidence is preliminary and the studies are small; this effect pertains primarily to HPMC (hypromellose) rather than to hyprolose (HPC) per se.

5.3 Use as a Pharmaceutical Excipient and Supplement Delivery Vehicle

Hydroxypropyl cellulose (HPC) is a water-soluble polymer used as a binder during pharmaceutical tableting and granulation. HPC is also known as a base material for pharmaceutical film by virtue of its film formability with excellent plasticity. In the supplement industry, HPC and HPMC are most commonly encountered as ingredients in capsule shells and tablet binders rather than as active ingredients.

Vegetable cellulose capsules are a type of capsule shell made from cellulose, a polysaccharide derived from plant fibers, commonly wood pulp or cotton linters. They serve as a widely used alternative to traditional gelatin capsules, which are animal-derived, making them suitable for vegetarian, vegan, halal, and kosher products. These capsules are primarily used as a delivery vehicle for encapsulating powders, liquids, or granules in dietary supplements and pharmaceuticals.

An HPMC–HPC combination is utilized in pharmaceutical film coatings, with HPC improving film adhesion. L-HPC is used as a binder and disintegrant in tablets or wafers containing dietary supplements of vitamins and/or minerals.

6. Body Systems and Health Areas

• Ocular system: Hyprolose usually reduces the signs and symptoms resulting from moderate to severe dry eye syndromes, such as conjunctival hyperemia, corneal and conjunctival staining with rose bengal, exudation, itching, burning, foreign body sensation, smarting, photophobia, dryness and blurred or cloudy vision.
• Gastrointestinal system (as excipient/fiber): When ingested, HPC behaves similarly to dietary fiber; it is poorly absorbed and passes largely unchanged through the gut. Viscous cellulose ethers in the HPMC class have demonstrated mechanistic activity in reducing cholesterol absorption in the small intestine.
• Cardiovascular system (HPMC class): Via its soluble fiber properties, the cellulose ether class (principally studied as HPMC) has demonstrated LDL cholesterol–lowering activity in clinical trials.
• Drug delivery and systemic bioavailability: HPC functions as a controlled-release matrix, influencing the rate of absorption of co-administered pharmaceutical agents and dietary supplement active ingredients.

7. Dosage Forms and Dosages Reported in Studies

7.1 Ophthalmic Insert

Each Lacrisert insert contains 5 mg of hydroxypropyl cellulose. Lacrisert contains no preservatives or other ingredients. It is about 1.27 mm in diameter by about 3.5 mm long.

One Lacrisert ophthalmic insert in each eye once daily is usually sufficient to relieve the symptoms associated with moderate to severe dry eye syndromes. Individual patients may require more flexibility; some patients may require twice daily use for optimal results. Clinical experience with Lacrisert indicates that in some patients several weeks may be required before satisfactory improvement of symptoms is achieved.

7.2 Oral Dietary Fiber Forms (HPMC/Related Class)

In the randomized cholesterol-lowering study, patients were administered placebo, 2.5, 5.0, or 7.5 g/day of HPMC for a 6-week treatment period. In the pilot dose-response study, HPMC-containing products delivered 3, 5, or 10 g of HPMC of low, moderate, moderately high, or high viscosity. These dosages pertain to HPMC/hypromellose rather than to hyprolose (HPC) specifically, and were administered in the context of a controlled dietary intervention.

7.3 Tablet and Capsule Excipient Forms

As a pharmaceutical excipient in tablets and capsules, HPC is employed in quantities determined by formulation requirements rather than therapeutic dosing. EFSA concluded there would be no safety concern as a food additive in food supplements in solid form (tablet), with a maximum use level of 20,000 mg/kg.

8. Regulatory Status

The safety of both HPC (E463) and L-HPC (E463a) as food additives has been approved by the U.S. Food and Drug Administration (FDA), the European Food Safety Authority (EFSA), and the Joint FAO/WHO Expert Committee on Food Additives (JECFA). HPC and L-HPC may be safely used in food and can be used as emulsifier or emulsifier salt, formulation aid, stabilizer or thickener, and texturizer in food.

JECFA (1990), the SCF (1994), and the EFSA ANS Panel (2018) all considered it unnecessary to set an Acceptable Daily Intake (ADI) for celluloses, including hydroxypropyl cellulose, based on low toxicity and negligible absorption in the human gastrointestinal tract. Cellulose and cellulose derivatives were evaluated for their safety by JECFA (1990), which allocated a group ADI of "not specified." The Scientific Committee for Food (SCF, 1994, 1999) also assessed five closely related cellulose derivatives, allocating a group ADI of "not specified." The last comprehensive evaluation for food additive use was done in 2017–2018 by the EFSA Panel, which concluded that there was no need to set a numerical ADI.

Both microcrystalline cellulose (E460i) and hydroxypropyl cellulose (E463) have been previously evaluated by the WHO/FAO Joint Expert Committee on Food Additives and by the former EU Scientific Committee on Food, resulting in the allocation of an ADI of "not specified" for both products. EFSA has recently re-evaluated the safety of hydroxypropyl cellulose (E463) and other celluloses and concluded that there was no need for a numerical ADI and that there would be no safety concern at the reported uses and use levels.

An "ADI not specified" was established for each modified cellulose E461–E466 and E469 by JECFA (1990, 1999).

9. Safety Considerations and Known Interactions

9.1 General Toxicological Profile

The additive is poorly absorbed by the human digestive system; most ingested HPC passes through the body largely unchanged. Toxicological studies have demonstrated low acute and chronic toxicity in animal models at relevant dietary exposure levels. The compound does not bioaccumulate in body tissues and is readily excreted.

Hydroxypropyl cellulose has been used in food production for decades with minimal documented safety concerns. The FDA has received zero adverse event reports specifically linked to HPC consumption, and no product recalls have been issued due to this additive. This safety record reflects both the compound's low toxicity profile and widespread use without reported complications.

9.2 Ophthalmic Adverse Reactions

The following adverse reactions have been reported in patients treated with Lacrisert, but were in most instances mild and transient: transient blurring of vision, ocular discomfort or irritation, matting or stickiness of eyelashes, photophobia, and hypersensitivity. If improperly placed, Lacrisert may result in corneal abrasion.

9.3 Oral/Gastrointestinal Adverse Effects

When hydroxypropyl cellulose is used in oral preparations, some sensitive individuals may experience mild digestive discomfort, such as bloating, mild diarrhea, or constipation. This is primarily related to its swelling due to water absorption in the intestines, similar to the effects of dietary fiber, and in most cases is a temporary condition.

9.4 Drug Interactions

Hydroxypropyl cellulose ophthalmic (Lacrisert) has no noted severe, serious, moderate, or minor interactions with any other drugs on record.

In oral formulations, there are two known physicochemical interactions of note. HPC may form weak physical encapsulation or complexation interactions with certain ionic drugs or nutrients, slightly reducing their absorption rate. However, these interactions are generally mild and do not result in serious clinical consequences. Additionally, for sustained-release formulations containing hydroxypropyl cellulose, if taken concurrently with high concentrations of alcohol, the alcohol may alter the gel layer structure, leading to premature drug release and causing the so-called "dose dumping" effect. While this situation is more common with other sustained-release excipients, caution is still warranted with HPC preparations.

9.5 Special Populations

Vegetable cellulose capsules (including HPC-based shells) are considered safe for special populations, including children, pregnant and lactating women, and are particularly suitable for vegetarians, vegans, and those with religious dietary restrictions. A very serious allergic reaction to hydroxypropyl cellulose is rare. However, symptoms of a serious allergic reaction, including rash, itching or swelling (especially of the face, tongue, or throat), severe dizziness, or trouble breathing, warrant immediate medical attention.

9.6 Regulatory Acceptability and Purity Standards

Due to its safe source and stable chemical properties, HPC is generally considered to have very low toxicity and has been listed as a safe excipient by the US FDA, the European Pharmacopoeia, and many other national and regional pharmacopeias. Hydroxypropyl Cellulose is a partially substituted poly(hydroxypropyl) ether of cellulose. It may contain not more than 0.60 percent of silica or other suitable anticaking agents.

References

• NIH PubChem: Hydroxypropyl Cellulose (Hyprolose) — Compound Summary
• USP–NF Monograph: Hydroxypropyl Cellulose (NF)
• USP: Hydroxypropyl Cellulose Pharmacopeial Discussion Group Stage 6 Sign-off
• USP: Low-Substituted Hydroxypropyl Cellulose Monograph
• NIH DailyMed: Lacrisert (Hydroxypropyl Cellulose Ophthalmic Insert) 5 mg — FDA Label
• EFSA Journal (2020): Safety and Efficacy of Hydroxypropyl Cellulose for All Animal Species
• EFSA Journal (2018): Re-evaluation of Celluloses E460–E469 as Food Additives
• PMC/EFSA (2020): Safety of Low-Substituted Hydroxypropyl Cellulose (L-HPC) as a Food Additive in Supplements in Tablet Form
• PubMed/Cornea (2010): Efficacy of Hydroxypropyl Cellulose Ophthalmic Inserts (Lacrisert) in Subsets of Patients with Dry Eye Syndrome — Luchs et al.
• PubMed/Cornea (2009): Extending the Duration of Tear Film Protection in Dry Eye Syndrome — Retrospective Case Series of HPC Ophthalmic Insert
• American Ophthalmological Society (2009): Hydroxypropyl Cellulose Ophthalmic Inserts Reduce Signs and Symptoms of Dry Eye Syndrome — McDonald et al.
• ScienceDirect/Journal of Clinical Lipidology (2009): Lipid-Altering Effects of Different Formulations of Hydroxypropylmethylcellulose — Maki et al.
• ScienceDirect/American Journal of Cardiology (1999): Cholesterol Lowering with High-Viscosity Hydroxypropylmethylcellulose
• PubMed (2007): Hydroxypropylmethylcellulose Significantly Lowers Blood Cholesterol in Mildly Hypercholesterolemic Human Subjects
• PMC/Pharmaceutics (2025): Hydroxypropyl Methylcellulose — A Key Excipient in Pharmaceutical Drug Delivery Systems
• FoodAdditives.net: What is Hydroxypropyl Cellulose (E463): Two Types, Uses, Safety, Side Effects
• AdditiveFacts: Hydroxypropyl Cellulose (E463): Safe per FDA & EFSA
• RxList: Lacrisert (Hydroxypropyl Cellulose Ophthalmic) — Side Effects, Uses, Dosage, Interactions
• Drugs.com: Lacrisert Dosage Guide
• Drugs.com International: Hyprolose — International Database