A promising strategy to overcome these problems involves the development of suitable drug carrier system. The In vivo fate of the drug is no longer mainly determined by the properties of the drug, but by the carrier system, which permit a controlled and localized release of the active drug according to the specific needs of the therapy. The size of the carrier depends on the desired route of administration and ranges from few nanometers to micrometers (implants). Implants and microparticles are too large for drug targeting and intravenous administration. Therefore, colloidal carriers have attracted increasing attention during recent years. Investigated systems include nanoparticles, nanoemulsions, liposomes, niosomes, nanosuspensions, micelles, and soluble polymer-drug conjugates.