Excipient Profile of HPMC: Hydroxypropyl Methylcellulose (HPMC), also known as hypromellose, is a semisynthetic, inert, and viscoelastic polymer. It is chemically denoted as C56H108O30.
Hydroxypropyl Methylcellulose (HPMC), a non-toxic and non-irritant material, has been widely used in the pharmaceutical industry due to its versatility and safety. This article aims to provide a comprehensive review of the excipient profile of HPMC, focusing on its role in drug delivery systems and its interaction with other excipients.
Excipient Profile of HPMC
Chemical Structure
HPMC is derived from cellulose, the main polysaccharide and constituent of plant cell walls and vegetable fibers. The cellulose backbone is made up of anhydroglucose units linked together by β-1,4-glycosidic bonds.
In HPMC, some of the hydroxyl groups in the anhydroglucose units are replaced by methoxy (-OCH3) and hydroxypropyl (-OCH2CHOHCH3) groups through a process called etherification. The degree of substitution with these groups can vary, leading to different grades of HPMC with different properties.
Excipient Profile of HPMC (Hydroxypropyl Methylcellulose)
| Property | Description |
|---|---|
| Chemical Formula | C56H108O30 |
| Molecular Weight | Variable, depending on the degree of substitution |
| Appearance | White to slightly off-white powder |
| Odor | Odorless |
| Taste | Tasteless |
| Solubility | Soluble in cold water, forms a viscous colloidal solution. Practically insoluble in hot water, organic solvents, and oils |
| Melting Point | Decomposes before melting, typically around 200°C |
| Boiling Point | Not applicable, as HPMC decomposes before boiling |
| Hygroscopicity | Yes, absorbs moisture from the air |
| pH Stability | Stable in a pH range of 3.0 to 11.0 |
| Viscosity | Depends on molecular weight, concentration, and temperature. Exhibits pseudoplastic flow |
| Biodegradability | Resistant to enzymatic degradation |
Physical and Chemical Properties
HPMC is a white to slightly off-white powder. It is odorless and tasteless. It is hygroscopic, meaning it absorbs moisture from the air. It is soluble in cold water, forming a viscous colloidal solution, but is practically insoluble in hot water, organic solvents, and oils.
The viscosity of HPMC in water solution is determined by its molecular weight, concentration, and temperature. It exhibits pseudoplastic flow, meaning its viscosity decreases with increasing shear rate. This property is beneficial in applications such as coatings and adhesives, where easy application is required.
HPMC is stable under alkaline conditions, and its viscosity is not significantly affected by pH in the range of 3.0 to 11.0. It is also resistant to enzymatic degradation, which makes it useful in controlled-release drug formulations.
Safety Profile
HPMC is considered safe for human consumption. It is non-toxic and non-irritant. It is not absorbed by the body but passes through the digestive tract unchanged. It has been approved by regulatory authorities worldwide, including the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA), for use in food and pharmaceutical applications.
In conclusion, the chemical profile of HPMC contributes to its wide range of applications in the pharmaceutical industry, from controlled-release tablets to transdermal patches, and beyond. Its safety, versatility, and stability make it a valuable excipient in drug formulation.
Role as a Binder
HPMC is commonly used as a binder in tablet formulations. It helps to hold the tablet together and gives it the necessary mechanical strength. The binding property of HPMC is due to the formation of a gel layer when it comes into contact with water. This gel layer acts as a matrix, entrapping the drug particles and other excipients, and holding them together.
Role as a Controlled-Release Agent
One of the most significant applications of HPMC in pharmaceutical formulations is its role as a controlled-release agent. HPMC-based matrices are widely used in the formulation of oral controlled-release dosage forms. When the matrix comes into contact with gastrointestinal fluids, the HPMC in the matrix hydrates and swells, forming a gel layer around the tablet.
The drug is then gradually released from the matrix through diffusion and erosion of this gel layer. The rate of drug release can be controlled by adjusting the concentration and viscosity grade of HPMC in the matrix.
Role as a Film Coating Agent
HPMC is also used as a film coating agent in tablets and granules. It forms a smooth, transparent, and glossy film that is resistant to cracking. The film coating serves several purposes: it can mask the taste and odor of the drug, protect the drug from moisture and light, enhance the appearance of the tablet, and provide a surface for printing.
Role as a Thickening Agent
In semi-solid and liquid formulations, HPMC is used as a thickening agent. It increases the viscosity of the formulation, which can improve the stability and texture of the product. This property is particularly useful in topical formulations, where it can enhance the spreadibility and adhesion of the product to the skin.
Role as a Stabilizer
HPMC can act as a stabilizer in suspensions and emulsions. It helps to prevent the settling or aggregation of particles, thereby maintaining the uniformity of the formulation.
Safety and Biocompatibility
HPMC is considered safe for human consumption. It is non-toxic, non-irritant, and biocompatible. It is not absorbed by the body but passes through the digestive tract unchanged. It has been approved by regulatory authorities worldwide for use in food and pharmaceutical applications.
In conclusion, the excipient profile of HPMC is characterized by its versatility and safety. Its unique properties make it a valuable excipient in a wide range of pharmaceutical formulations.
Role in Ophthalmic Formulations
HPMC is a key ingredient in many ophthalmic formulations due to its lubricating and viscosity-enhancing properties. It is used in artificial tears and other eye drops to provide relief from dry eyes. The high viscosity of HPMC solutions helps to prolong the contact time of the formulation with the eye surface, thereby increasing the effectiveness of the active ingredients.
Role in Mucoadhesive Formulations
HPMC has excellent mucoadhesive properties, which makes it useful in the formulation of buccal, nasal, ocular, and vaginal drug delivery systems.
The mucoadhesive property of HPMC is due to its ability to form hydrogen bonds with the mucin present in mucus. This allows the formulation to adhere to the mucosal surface for an extended period, thereby enhancing the absorption of the drug.
Role in Transdermal Patches
HPMC is used in the formulation of transdermal patches due to its film-forming and drug release-modifying properties. A recent study demonstrated the formulation of transdermal patches of Clotrimazole using EC and HPMC in different ratios.
The research found that the in-vitro release profiles of the formulations showed differences depending on the composition, highlighting the role of HPMC in enhancing drug diffusion through the skin.
Role in 3D Printing of Pharmaceuticals
The advent of 3D printing technology in the pharmaceutical industry has opened up new possibilities for the use of HPMC. A recent study presented a unique method of fabricating gastro-floating tablets using semisolid extrusion (SSE) 3D printing with HPMC.
The results showed that all fabricated gastro-floating tablets could float for over 10 hours, indicating the effectiveness of HPMC in this novel drug delivery system.
Conclusion
The excipient profile of HPMC is characterized by its versatility, safety, and biocompatibility. Its unique properties make it a valuable excipient in a wide range of pharmaceutical formulations, from traditional dosage forms like tablets and capsules to novel drug delivery systems like transdermal patches and 3D printed tablets. As research continues, the potential for novel applications of HPMC in the pharmaceutical industry continues to grow.
References
- Roy, P. K., Subba, R., Kalita, N., Remlalruali, Zonuntluangi, Laldinchhana, Devi, S. H. V., Lalhriatpuii, T. C., & Lalhlenmawia, H. (2023). Effect of Hydroxypropyl Methylcellulose (HPMC) in Release Profile of Air Fresheners Gel Prepared Using Carrageenan and HPMC. International Journal of Pharmaceutical Sciences Review and Research. DOI: 10.47583/ijpsrr.2023.v79i02.027
- Allenspach, C., Timmins, P., Sharif, S., & Minko, T. (2020). Characterization of a novel hydroxypropyl methylcellulose (HPMC) direct compression grade excipient for pharmaceutical tablets. International Journal of Pharmaceutics. DOI: 10.1016/j.ijpharm.2020.119343
- Miranda, A., Millán, M., & Caraballo, I. (2007). Investigation of the Influence of Particle Size on the Excipient Percolation Thresholds of HPMC Hydrophilic Matrix Tablets. Journal of Pharmaceutical Sciences. DOI: 10.1002/jps.20912
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