[Improvement of drug bioavailability using protease inhibitors].

Although many proteins and peptides were produced by gene-technology, their administration routes are limited to be i.v. route. To increase the clinical use of these products, oral dosage form is required. However, in the case of oral administration, proteins are degraded by digestive fluid having strong protease activity. To decrease the protease activity, protease inhibitors are administered concomitantly with proteins. Aprotinin, soybean trypsin inhibitors and gel-forming polymer such as Polycarbophil are representative protease inhibitors. Gel-forming polymers have both protease inhibiting activity and absorption enhancing effect on protein/peptides. The usefulness of these protease inhibitors have been suggested as an additive for the oral delivery of G-CSF and vasopressin derivatives.