Evaluation of physical stability and drug content of zoledronate bisphosphonate gel

Introduction
The gel emulsion form of zoledronate bisphosphonate has been proven to increase the number of osteoclasts via apoptosis when applied topically. The gel form is commonly used for topical application in the oral cavity.

Objectives
We aimed to evaluate the physical stability of zoledronate bisphosphonate in its gel form to assess its suitability for clinical application.

Material and methods
The gel formulation was prepared using carboxymethylcellulose, glycerine, and sodium benzoate in a dosage form of 40 μg of zoledronate per 25 mg of the gel. The prepared gels were stored at 25°C and 40°C for 28 days and evaluated for viscosity, pH value, spreadability, adhesive strength, and drug content on days 1, 7, 14, and 28 of incubation.

Results
Throughout the study, at 40°C of storage, the gel demonstrated significantly increasing viscosity and adhesive strength, but decreasing spreadability. However, the pH and drug content decreased at 25°C and 40°C.

Conclusion
Zoledronate bisphosphonate gel showed stability in physical characteristics and drug content when stored at 25°C for 28 days.