Clinical pharmacology: proteins for the transport of drugs

Most drugs have to pass cellular barriers in order to reach their site of a ction. This can be accomplished passively by diffusion, but more often it i s an energy-consuming process using specific carrier proteins. Two groups o f such proteins which are well characterised, the organic cation transporte rs and the multidrug resistance proteins, are discussed in detail in the pr esent review. The clinical significance of these proteins is due not only t o their role in drug distribution and elimination, but also to possible dru g interactions when different drugs and/or endogenous substrates compete wi th the same carrier protein. Inhibition of multidrug resistance proteins co uld be of therapeutic value in impairing transport of drugs from their site of action and this could be particularly beneficial in the treatment of ma lignant diseases.