Evaluation of the pharmaceutical characteristics of various enteric-coated aspirin tablets under different storage conditions.

The formulation characteristics of 6 brands of enteric-coated aspirin tablets under unpackaged conditions at 40°C and 60°C for 4 weeks were analyzed. Appearance, salicylic acid content, dissolution rates, and surface properties (by Raman microscopy) were evaluated to determine stability data, taking into account the clinical use of generic drugs. No change in appearance, decomposition, or dissolution rates was observed in unpackaged aspirin tablets stored at 40°C for 4 weeks. However, when stored at 60°C, tablets of 5 of the 6 brands showed whiskers on their surfaces along with an increase in salicylic acid content and a decrease in dissolution rate. Results of Raman mapping on the surface and cross sectional surface of the tablets with whiskers showed a salicylic acid peak associated with storage at 60°C for 4 weeks. However, for tablets from 1 of the 6 brands, no salicylic acid peaks were observed. For this tablet, Raman microscopy revealed 2 layers of film coating, and talc, which greatly affected the stability of the acetylsalicylic acid, was found only in the outer layer film. These results indicated that the protection of compatibility with talc is one of the important factors in enhancement of aspirin tablet stability in this tablet. We concluded that certification of the characteristics associated with stability and formulation is essential for generic drugs, which are not required to undergo stability testing under extreme storage conditions.