OBJECTIVE To analyze the content of related substances and 5-hydroxymethylfurfural(5-HMF) in dextromethorphan hydrobromide and guaifenesin syrup, and investigate the intrinsic quality of the syrup.

METHODS  The related substances and 5-HMF in 11 batches of dextromethorphan hydrobromide and guaifenesin syrup were determined by HPLC. The separation was performed on Agilent Zorbax Bonus-RP(4.6 mm×250 mm, 3.5 µm) column with gradient elution of 0.2% trifluoroacetic acid solution(mobile A)-acetonitrile(mobile B) at a detection wavelength of 278 nm to determine the principal components and various impurities. Investigated the changes of impurities and analyzed the influencing factors according to the forced destruction test of raw materials and the accelerated test of syrup.

RESULTS The principal component and each impurity were adequately separated. The correlation coefficient of each impurity was ≥ 0.9994 and the recovery was greater than 95%. The impurities increased significantly in products with low pH and insufficient packaging shading.

CONCLUSION The content of degradation impurities in dextromethorphan guaifenesin syrup is impacted by pH and packaging materials. It is suggested that the pH of dextromethorphan hydrobromide and guaifenesin syrup should be controled and shading materials package should be used to reduce the increase of impurities.