Abstract: OBJECTIVE To investigate the effect of the duration of storage under (75±5)% relative humidity(RH) on the dissolution rate of two formulations of clopidogrel bisulfate tablets, providing reference for investigating abnormal data in the drug dissolution curve. METHODS Samples of preparation 1 and preparation 2 of clopidogrel bisulfate tablets were placed in sealed sample boxes and stored in an environment with 75% RH simulated by saturated sodium chloride for 1, 2, and 3 h. The dissolution curves and moisture content were measured and compared with the dissolution curves of samples without humidity absorption using a non-model dependent similarity factor. RESULTS Samples of preparation 1 were dissimilar to 0 h after 2 h of storage under (75±5)% RH, while samples of preparation 2 were still similar after 4 h of storage. Moisture content of the preparation 1 increased faster than that of preparation 2 within 3 h and continued to increase within 5 h, while moisture content of preparation 2 increased more slowly after 2 h. CONCLUSION Preparation 1 contains more crosslinked polyvinylpyrrolidone as a disintegrant than preparation 2, which makes it more sensitive to changes in environmental humidity. Therefore, the impact of environmental humidity should be considered for such formulations in both storage and testing.