Hydroxypropyl Methylcellulose (HPMC) is a semi-synthetic nonionic cellulose ether widely used in the pharmaceutical industry, especially in tablet formulations. Due to its excellent film-forming, adhesive, thickening and sustained-release properties, HPMC plays multiple key roles in tablet preparation.
1. As a binder (Binder)
HPMC has good adhesive properties and can tightly bind powdered drugs and excipients to form particles with a certain hardness, thereby improving compressibility during tableting. Compared with traditional binders (such as starch slurry or PVP), HPMC has the following advantages:
Good water solubility: It can be dispersed in cold water to form a viscous solution, suitable for wet granulation.
Low hygroscopicity: Reduces moisture absorption of tablets during storage and improves stability.
Does not affect disintegration: When used in moderation, it will not excessively prolong the disintegration time of tablets.
The bonding effect of HPMC depends on its molecular weight and concentration. Low-viscosity models (such as E5 and E15) are usually used as adhesives.
2. As a sustained-release matrix material (Matrix Former)
HPMC is one of the core excipients for the preparation of sustained-release tablets. Its hydrophilic gel properties can be used to control the drug release rate. The mechanism of action is as follows:
Gel layer formed when in contact with water: After the tablet surface contacts body fluids, HPMC absorbs water and swells to form a gel barrier, and the drug is slowly released through diffusion or gel erosion.
Adjustable release rate: By changing the viscosity grade (such as K4M, K15M, K100M) or dosage of HPMC, the drug release rate can be adjusted to achieve a sustained release effect of 12 to 24 hours.
HPMC-based sustained-release tablets are suitable for water-soluble and poorly soluble drugs, such as metformin hydrochloride sustained-release tablets, nifedipine controlled-release tablets, etc.
3. As a film coating material (Film Coating Agent)
HPMC is a common film-forming material for tablet film coating. Its main functions include:
Improving appearance: providing a smooth and uniform coating layer to cover up the bad smell or color of the drug.
Moisture protection: reducing the impact of environmental humidity on the tablet core and improving stability.
Regulating release: in combination with plasticizers (such as PEG) or other polymers (such as ethyl cellulose), enteric or sustained-release coatings can be prepared.
The commonly used HPMC coating models are E5 and E15, which are usually used together with pigments and sunscreens (such as titanium dioxide).
4. As an auxiliary component of disintegrants (Disintegrant)
Although HPMC itself is not a highly efficient disintegrant, it can work synergistically with other disintegrants (such as cross-linked carboxymethyl cellulose sodium) in specific formulations:
Optimizing swelling: The swelling ability of HPMC can promote the formation of pores inside the tablet and accelerate water penetration.
Reducing the negative effects of binders: When HPMC is used as a binder, the dosage needs to be controlled to avoid excessive delay in disintegration.
5. Improve drug dissolution
For poorly soluble drugs, HPMC can improve dissolution through the following mechanisms:
Inhibit drug crystallization: as a carrier in solid dispersions, maintain the amorphous state of the drug.
Increase wettability: the gel layer promotes the contact between the drug and the dissolution medium.
Key factors for selecting HPMC
Viscosity grade: low viscosity (3-15 cP) is used for adhesives or coatings, and high viscosity (4000-100000 cP) is used for sustained-release matrices.
Degree of substitution: affects solubility and gel strength and needs to be adjusted according to the properties of the drug.
HPMC is a multifunctional excipient in tablet formulations, with multiple functions such as bonding, sustained release, coating and improved dissolution. Its high safety (FDA approved) and wide applicability make it an indispensable material in the development of modern solid preparations. Reasonable selection of HPMC models and proportions can optimize the process performance, stability and therapeutic effects of tablets.
Post time: Apr-08-2025