Buparvaquone mucoadhesive nanosuspension: preparation, optimisation and long-term stability.

The poorly soluble drug buparvaquone is used in experimental clinics against the gastrointestinal persisting parasite Cryptosporidium parvum. It was produced as nanosuspension by high pressure homogenisation. Main advantages of nanosuspensions (amongst others) are their increase of saturation solubility and dissolution velocity, improving the bioavailability of drugs. The buparvaquone nanosuspension had a bulk population of about 600 nm (analysed by photon correlation spectroscopy (PCS)). The additional analysis performed with laser diffraction showed that only a very small content of microparticles occurred, which is, for the special features of nanosuspensions, negligible because they were still below 3 microm. Another feature of nanosuspensions is the adhesion properties to surfaces, e.g. mucosa. To further increase the adhesion time of the buparvaquone nanosuspension to C. parvum, the nanosuspension was formulated with hydrogels made from mucoadhesive polymers, e.g. different types of Carbopol and chitosan. Only a small increase of the particle size of the bulk population occurred directly after the incorporation of buparvaquone nanosuspension into the hydrogels. The nanosuspension/hydrogel systems were physically long-term stable over a period of 6 months as indicated by the unchanged particle sizes.