Formulation and in vitro evaluation of in situ gels containing secnidazole for vaginitis.

Gel dosage forms are successfully used as drug delivery systems considering their ability to prolong the drug release. The main objective is to formulate and evaluate in situ vaginal gels of secnidazole, based on ion activated systems. The system utilizes polymers that exhibit sol-to-gel phase transition due to change in specific physico chemical parameters. Ion triggered system using gellan gum (0.1-0.75% w/v) along with sodium carboxymethylcelluose was used to prolong the release of secnidazole (1% w/v). Formulations were evaluated for gelling capacity, viscosity, gel strength, mucoadhesive force, spreadability, microbiological studies and in vitro release studies. The transformation of sols occur in the presence of monovalent/divalent cations in the dissolution medium. Effect of calcium carbonate and other process parameters were optimized and found that increase in calcium ions produce stronger gels. The drug content, clarity, and pH of formulation were found to be satisfactory. The viscosity was found to be in the range of 0.005 to 0.085 for sols, whereas for the gels 16 Pa.s. Formulation showed pseudoplastic flow with thixotrophy. The gel strength (using texture analyzer) and mucoadhesion was found to be up to 6.5 g and 4 g respectively. The optimized formulations were able to release the drug for 360 min. The gels are expected to improve the administration at the site of infection and decrease frequency.