| abstract |
The present invention relates to dosage forms of orally administered drugs for release to the colon, comprising a drug enclosed in a crosslinked hydrogel which exhibits pH dependent swelling and which is composed of an ionizable comonomer such as acrylic acid, a non-ionizable comonomer such as an acrylamide, and a crosslinking agent which contains an aromatic azo bond. The selective release of the drug into the colon is carried out thanks to the combination of the pH-dependent swelling properties specific to the hydrogel and to the degrading properties of said hydrogel by enzymatic splitting of the azo bonds effected by the azoreductases. |