Determination of Intrinsic Dissolution Rate and Permeability of Two Crystal Forms of Zolpidem Tartrate in vitro
The solubility and dissolution characteristics of two crystal forms(A and D)of zolpidem tartrate(1)were investigated.Firstly,the two crystal forms were characterized by XRD and DSC.The results showed that they had different crystal structures and thermodynamic properties.Subsequently,the apparent dissolution rates and intrinsic dissolution rates of crystal forms A and D were measured in various pH media(water,0.01 mol/L hydrochloric acid,pH 4.5 acetate buffer,and pH 6.8 PBS).The results showed that there were significant differences in the apparent dissolution rate,apparent solubility,and intrinsic dissolution rate between the two crystal forms in pH 6.8 PBS.According to the test results,both crystal forms of 1 showed the high solubility.The results of the parallel artificial membrane permeation test showed that the effective permeability coefficient of 1 was 8×10-5-9×10-5 cm/s,indicating they had high permeability.Although both crystal forms in this study could be classified to BCS class Ⅰ drugs,there were certain differences in solubility and dissolution rates,crystal structure,and melting point,which should be given some references for screening the crystal forms of drug substance in formulation development.
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