Enhanced hypotensive effect of nimodipine solid dispersions produced by supercritical CO2 drying

• Solid dispersions of nimodipine and PVP were prepared by supercritical CO2 drying.
• The physicochemical characteristics of the samples depended on the carrier ratio.
• All solid dispersions increased the solubility and dissolution rate of the drug.
• A significant hypotensive effect was observed for the sample with 90% of PVP.

Solid dispersions of nimodipine and PVP K-30 were prepared by supercritical fluid technology at three drug:carrier ratios (1:9, 2:8, 3:7, w/w). The samples were characterized by X-ray powder diffraction, infrared spectroscopy and scanning electron microscopy, and evaluated by means of their solubility, dissolution rate and hypotensive effect. The solid dispersion with the highest amount of PVP K-30 (SD 1:9) presented an amorphous state, a porous surface and hydrogen bonds between nimodipine and the carrier. On the other hand, the other solid dispersions were semicrystalline. All formulations enhanced the solubility and dissolution rate of nimodipine and the best results were found for SD 1:9. This formulation promoted an increase of more than 1300% in the solubility of nimodipine, besides releasing 100% of the drug within 5 min. When submitted to in vivo studies SD 1:9 decreased significantly the mean arterial pressure and also reduced its phenylephrine-induced increase.

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