Hydrogels Formed by Cross-Linked Polyvinylalcohol as Colon-Specific Drug Delivery Systems

Abstract

Polyvinylalcohol (PVA) of different molecular weights was cross-linked with succinyl, adipoyl, or sebacoyl chloride to obtain hydrogel-forming polymers and to determine their suitability as colon-specific drug delivery systems. Diclofenac sodium, propranolol hydrochloride, and vitamin B6 hydrochloride were used as hydrophilic model drugs with colon-specific release that should yield high concentrations in the large intestine, minimizing release in the upper part of the gastrointestinal tract. Spray-dried mixtures of the drugs and the polymer (at a 1 : 2 w/w ratio) were prepared, and the release of the drugs from the mixtures was evaluated in vitro at pH 2.0, 5.5, and 7.4. The results indicated the ability of the cross-linked polymers to slow the release of the drugs analyzed with respect to the pure drug dissolution at each pH. The lengthening of the cross-linker acyl chain was noted to decrease drug release further.

Key Words:

• Colon-specific release
• Cross-linked polyvinylalcohol
• Hydrogels
• Hydrophilic drugs
• Spray-dried mixtures