Two lots (3 samples each) of 4 companies’(Shionogi&Co.,Ltd.,Meiji Seika Kaisha,Ltd.,Nichi-iko Pharmaceutical Co.,Ltd.and Merck Pharmaceutical Co.,Ltd.) vancomycin hydrochloride injection products (referred to hereafter as VCM injections) were dissolved in normal saline 100 mL.The solubility of each product was investigated for 3 different dissolution times (5 seconds,10 seconds,30 seconds) using a bioassay method employing Bacillus subtilis ATCC 6633 and a fluorescence polarization immunoassay.
The dissolution rate of the Shionogi product increased from 83.9±2.8% at 5 seconds to 99.0±0.7% at 30 seconds which was in proportion to the increase in dissolution time.Further,the dissolution rates for the Meiji Seika Kaisha and Nichi-Iko Pharmaceutical products were 90% or more for a dissolution time of 30 seconds.On the other hand the dissolution rate of the Merck Pharmaceutical product,which was 81.7±2.6% for a dissolution time of 10 seconds,was only 83.1±2.8% for a dissolution time of 30 seconds.These results show that in order to obtain dissolution rates exceeding 90%,at least 30 seconds of dissolution time is required even for the VCM injection products manufactured by Shionogi,Meiji Seika Kaisha and Nichi-Iko Pharmaceutical.Moreover,as there were differences in the solubility of preparations,this should be taken into account when selecting the product.