Preparation and evaluation of solid dispersion for nitrendipine-carbopol and nitrendipine-HPMCP systems using a twin screw extruder.

In the present study, we prepared solid dispersions of the poorly water-soluble drug nitrendipine (NIT) using the twin screw extruder method with high-molecular-weight substances, hydroxypropylmethylcellulosephthalate (HPMCP) and Carbopol (CAR), as carriers. Powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) evaluation showed that solid dispersions can be formed when NIT-HPMCP and NIT-CAR mixtures are treated with the twin screw extruder method. Fourier Transformation IR Spectroscopy (FT-IR) obtained with NIT-HPMCP and NIT-CAR solid dispersions indicated the presence of hydrogen bonding between the drug and the carriers. NIT-CAR solid dispersions were found to give somewhat higher dissolution than crystalline NIT and physical mixtures, while the dissolution of NIT-HPMCP solid dispersions was markedly decreased compared with the crystalline NIT and physical mixtures. These findings indicated that CAR has a greater ability to improve the dissolution of NIT than HPMCP when a twin screw extruder was employed to prepare the solid dispersions. The twin screw extruder method can be used as a simple and effective method for the preparation of solid dispersions to improve the dissolution properties of poorly water-soluble drugs when choosing proper polymers as carriers.