Assessment of blending ratio of powdered medicine mixtures by image analysis

In the dispensing process, powdered medicines are often blended with diluents or different kinds of powder. With blending, the mass percent of the medicine in the mixture is unknown until the active pharmaceutical ingredient is determined with techniques such as spectroscopy and chromatography. However, pharmacists need to confirm the exact blending ratio of the dispensing mixture in pharmacies. We aimed to develop a precise and concise method to measure the mass percent of powdered medicine mixtures without an expensive analytical apparatus. Digital photographs of three kinds of mixture of lactose powder, as diluents, with Adona®, Anginal®, or Asverin® powder were taken with a microscope at a 30× magnification. Thereafter, the mass percent was calculated from digital images of the mixture using calibrated color information in the YCbCr color space. A linear regression, between the mass percent and color difference signal, Cb, value was obtained from 10 to 90% of the medicines (r(2)=0.9806-9993) in all systems. The intra-day accuracy and precision were 0.67-12% (relative error) and <5% (relative standard deviation), respectively. Moreover, the mass percent measured using image analysis was consistent with the concentration of the active pharmaceutical ingredient determined spectrophotometrically. This effective image analysis method enables pharmacists to nondestructively ensure the exact mass percent of the medicine in the dispensing mixture in pharmacies.