Optimization of film-coating formulation containing a novel low molecular weight hypromellose to achieve balanced tablet-coating performance


In recent years, a novel low molecular weight hypromellose (hypromellose 2906, VLV hypromellose) was developed to improve tablet-coating process and lower costs in the pharmaceutical industry. Such VLV hypromellose imparted economic, environmental, and performance benefits to the coating process and final products. However, there were still some concerns about this polymer in regard to weak mechanical strength of films and resultant stability issues of film coatings on tablets. In this study, a tablet-coating formulation was optimized using Box–Behnken design via blending conventional hypromellose with VLV hypromellose to achieve balanced coating performance in terms of highly productive coating, no sticking issues under mild coating conditions, and robust tablet film coatings in an accelerated stability study. By addition of only 5 wt% of conventional hypromellose (3.35 wt% HPMC E50 and 1.65 wt% HPMC E3), the film elongation and toughness index of optimized VLV hypromellose formulation increased by 154% and 372%, respectively, while the solution viscosity was still suitable for spray coating. The results of the following tablet-coating trials and stability study revealed that the stability and quality of tablet film coatings were significantly improved using this optimized VLV hypromellose-coating formulation, while a highly productive coating process and mild coating conditions without “sticking” issues were maintained simultaneously to the utmost extent.