Evaluation of properties microcrystalline chitosan as a drug carrier. Part 1. In vitro release of diclofenac from mictocrystalline chitosan hydrogel.

The influence of microcrystalline chitosan hydrogel, alone (MCCh) as well as in combination with methylcellulose (MC) or Carbopol (CP), on the release of diclofenac free acid (DA) and its salt (DS) was studied in vitro. Commercial Olfen gel (Mepha Ltd., Switzerland) was applied as a reference preparation. The influence of hydrophilizing agents (1,2-propylene glycol and glycerol) and methycellulose hydrogel on the rheological properties of the vehicle and on the release of drug from modified MCCh hydrogel was studied. The quantity of the released substance was determined by UV-spectroscopy. The results confirmed that release was dependent on the chemical character of the drug and on the type of vehicle. The process of diclofenac release from MCCh hydrogels as well as from Carbopol hydrogels runs in two phases. The first phase is characterised by rapid release whereas in the second phase the release is much slower. The most suitable basis for diclofenac is microcrystalline chitosan hydrogel with addition glycerol, 1,2-propylene glycol, and methylcellulose hydrogel.