Effect of hydrophilization of hydrophobic drugs on release rate from capsules.

The release of poorly soluble hydrophobic drugs from capsules can be improved significantly by the creation of a hydrophilic surface by intensive mixing of the hydrophobic drug with a small amount of a solution of a hydrophilic excipient. This technique was introduced previously for the production of microgranules. The data presented indicate that the hydrophilic material is mechanically distributed over the hydrophobic surface. The creation of hydrophilic capillaries in a capsule or tablet allowed the rapid penetration of the dissolution fluid, resulting in a dispersion of well-wetted particles, so that the maximum surface area of the powder was exposed to the dissolution medium. Moreover, hydrophilization of hydrophobic drugs has the important benefit that the release rate from capsules is independent of the surface tension of the dissolution medium.