Development and evaluation of novel solid nanodispersion system for oral delivery of poorly water-soluble drugs.

The aim of the present study was to develop and evaluate a novel drug solubilization platform (so-called solid nanodispersion) prepared by a simple co-grinding and solvent-free process. Using structurally diverse model compounds from the Pfizer drug library, including ingliforib, furosemide and celecoxib, we successfully prepared stable solid nanodispersions (SNDs) without the use of solvent or heat. Stable colloidal particles (<350 nm) containing drug, polyvinylpyrrolidone (PVP) K12 and sodium dodecyl sulfate (SDS) in 1:2.75:0.25 ratio were produced after 2 h of co-grinding. The composition and particle size of SNDs were optimized by varying the grinding media size, powder-to-grinding media ratio, milling speed and milling time. The resulting formulations contained crystalline drug and were stable at room temperature for over one month. Greater than 80% of the drug was released from the SND in less than 30 min, with sustained supersaturation over 4 h. Using furosemide (BCS class IV compound) as a model compound, we conducted transport studies with Madin-Darby canine kidney cells transfected with human MDR1 gene (MDCK/MDR1), followed by pharmacokinetics studies in rats. Results showed that the SND formulation enhanced the absorptive flux of furosemide by more than 3-fold. In the pharmacokinetics studies, the SND formulation increased C(max) and AUC of furosemide by 36.6 and 43.2 fold respectively, relative to Methocel formulation. Interestingly, physical mixture containing furosemide, PVP K12 and SDS produced a similar level of oral exposure as the SNDs, albeit with a longer T(max) than the SND formulation. The results suggest that PVP K12 and SDS were able to increase the furosemide free fraction available for oral absorption. Low solubility, poor permeability, and high first-pass effect of furosemide may also have produced the effect that small improvements in solubilization resulted in significant potentiation of the oral exposure of the physical mixture. However the use of a physical mixture of drug, polymer and surfactant, to increase drug bioavailability cannot be generalized to all drugs. There are only a few reported cases of such phenomenon. While SNDs may not be the only option to solubilize compounds in every case, SNDs are expected to be applicable to a broader chemical space of pharmaceutical compounds compared to a physical mixture. Ultimately, the formulation scientist will have to exercise judgment in choosing the appropriate formulation strategy for the compound of interest. SNDs represent a significant improvement over current enabling technologies such as nanocrystal and spray-dried dispersion technologies, in that SNDs are simple, do not require solvent or heat, are applicable to a structurally diverse chemical space, and are readily amenable to the development of solid dosage forms.