Formulation and Evaluation of in situ Gels Containing Clotrimazole for Oral Candidiasis

Gel dosage forms are successfully used as drug delivery systems to control drug release and protect the medicaments from a hostile environment. The main objective is to formulate and evaluate in situ oral topical gels of clotrimazole based on the concept of pH triggered and ion activated systems. The system utilizes polymers that exhibit sol-to-gel phase transition due to change in specific physico-chemical parameters. A pH triggered system consisting of carbopol 934P (0.2-1.4% w/v) and ion triggered system using gellan gum (0.1-0.75% w/v) along with hydroxylpropylmethylcelluose E50LV was used to prolong the release of clotrimazole (0.1% w/v). Formulations were evaluated for gelling capacity, viscosity, gel strength, bioadhesive force, spreadability, microbiological studies and in vitro release. The use of carbopol as in situ gel forming system was substantiated by the property to transform into stiff gels when the pH was raised, whereas in gellan gum this transformation occurred in the presence of monovalent/divalent cations. Effect of calcium carbonate and other process parameters optimized and found that increase in calcium ions produced stronger gels. The drug content, clarity, and pH of the formulation were found to be satisfactory. The viscosity was found to be in the range 5 to 85 centipoise for the sol, whereas for the gels it was up to 16000 centipoise. The formulation showed pseudoplastic flow with thixotrophy. The maximum gel strength (using texture analyzer) and bioadhesion was found to be up to 6.5 g and 4 g, respectively. The optimized formulations were able to release the drug up to 6 h. The formulation containing gellan gum showed better sustained release compared to carbopol based gels.