Patent ID: 9663439
Date: 2017-05-30
CPC Classifications: A61K,A61P,C07B,C07C,C07D

Claim:
1. A method for preparation of an Aildenafil citrate crystal form O, exhibiting a powder X-ray diffraction (PXRD) determination, wherein a table diffraction angles 2θ with an error of +/−0.2, D values and relative intensities is provided as follows: the method comprising: dissolving the Aildenafil citrate in 25 to 26 times (weight-volume ratio, g/ml) of a mixture of distilled water and tetrahydrofuran, wherein tetrahydrofuran takes 5% to 10% of a volume of the mixture; stirring and heating to reach the reflux temperature; filtering after 15 min to 20 min while heating, and cooling a filtrate to room temperature by stirring; insulating heat and stirring for 24 h to 26 h, precipitating and crystallizing, filtering and drying.