Optimizing the formulation ratio of HPMC in tablet coating is a complex process that involves understanding the physical and chemical properties of HPMC and how to achieve the desired coating performance by adjusting the formulation.
Choose the appropriate HPMC viscosity specification: HPMC has a variety of viscosity specifications. HPMC with different viscosities will affect the solid content and film-forming properties of the coating. Low viscosity HPMC helps increase solids content, but may need to be combined with other grades of HPMC to take advantage of their different physical properties.
Use a combination of multiple HPMC specifications: In optimized formulas, several HPMCs of different specifications are usually used simultaneously to comprehensively utilize their different physical properties. This combination improves coating efficiency and quality.
Adding plasticizers: Plasticizers such as polyethylene glycol (PEG), triethyl citrate, etc. can improve the flexibility of the film and reduce the glass transition temperature (Tg), thereby improving the physical properties of the coating.
Consider the concentration of the coating solution: The solid content of the coating solution has a significant impact on coating efficiency. Coating liquid with high solid content can reduce coating time and improve production efficiency. For example, when using Kollicoat® IR-based materials, coating formulation concentrations can be as high as 30%.
Optimize coating process parameters: Coating process parameters, such as spray rate, inlet air temperature, pot temperature, atomization pressure, and pot speed, will affect coating quality and uniformity. By adjusting these parameters, optimal coating results can be achieved.
Use of new low molecular weight HPMC: New low molecular weight HPMC (such as hypromellose 2906, VLV hypromellose) can improve the tablet coating process and reduce costs. By blending with conventional HPMC, balanced coating properties can be obtained in high-throughput coatings, no sticking issues under mild coating conditions, and robust tablet film coating.
Consider the stability of the coating material: HPMCP is a highly stable polymer whose stability is maintained under high-humidity conditions, which is critical to ensuring the quality of coated tablets during storage.
Adjust the preparation method of the coating solution: In the case of directly preparing the mixed solvent, gradually add HPMCP powder to the mixed solvent to avoid the formation of agglomerates. Other ingredients in the coating solution such as plasticizers, pigments and talc also need to be added as needed.
Consider the properties of the drug: The solubility and stability of the drug will influence the choice of coating formulation. For example, for photosensitive drugs, opacifiers may be needed to protect the drug from degradation.
Conduct in vitro evaluation and stability studies: Through in vitro dissolution testing and stability studies, the performance of coated tablets can be evaluated to ensure the effectiveness and stability of the coating formula in practical applications.
By comprehensively considering the above factors and adjusting according to specific production conditions and drug characteristics, the formula ratio of HPMC in tablet coating can be optimized to achieve efficient, uniform and stable coating effects.