Preparation and evaluation of isosorbide mononitrate hydrogels for topical fissure treatment

The aim of the present study was to prepare and evaluate hydrogels containing 0.1% isosorbide mononitrate (ISMN) for topical treatment of anal fissure. The hydrogels were prepared on the base of Carbopol 940, Poloxamer 407 or their combination. The highest viscosity and significant thyxotropy were observed for the combined hydrogel, which corresponded with slow drug release. Drug release from Poloxamer hydrogel was slow probably due to the heterogeneous structure of the gel - hydrophobic polyoxypropylene domains and hydrophilic polyoxyethylene domains. Drug release form Carbopol hydrogel was faster, which was associated with the lower viscosity and homogeneous gel structure. Further, Carbopol gel containing 0.1% ISMN (wt/wt) was tested on 21 patients with two applications daily for a period of 6 weeks. The results showed that chronic anal fissures healed in 71% of the patients. The formulation based on Carbopol seemed to be appropriate and efficient for the topical mononitrate treatment of anal fissures.