Development and In vitro Evaluation of Nifedipine Gel Formulations for Anorectal Applications

Objective: Current study focuses on the formulation and characterization of lipophilic and hydrophilic gel formulations of nifedipine to treat anal fissure via anodermal application. Methods: Lipophilic gels were prepared with Aerosil grades as gelling agents in bulk oils. Polyethylene glycols, hydroxypropyl methylcellulose, and Carbopol® 974P were used as gelling agents in water and propylene glycol for forming hydrophilic gels. The effect of repeated Freeze-Thaw Cycles (FT-C) on microstructures of the gels was investigated by examining viscosity, rheology and textural properties. Aerosil 200 containing lipophilic gels exhibited thixotropic behavior with plastic flow properties and higher viscosities. Result: Accordingly, their compressibility and adhesiveness increased. FT-C caused notable changes in microstructures and textural properties of the lipophilic gels excluding the formulation containing Aerosil 200-in-isopropyl myristate. Among the hydrophilic gels, the viscosity of Carbopol® 974P gels increased depending on the amount of polymer, triethanolamine and water; these gels featured plastic flow without thixotropic behavior. Their compressibility and adhesiveness were higher than other gel formulations with stable post-FT-C characteristics. The higher flux values of nifedipine were observed from water containing Carbopol® 974P gel. Conclusion: The results of the stability tests showed that the Carbopol® 974P gel had a longer shelf life than the Aerosil 200-in-isopropyl myristate gel.