(T1430-04-21) In Vitro Evaluation of Foamable Diclofenac Sodium Loaded Topical Microemulsion

Purpose: Diclofenac sodium (DS) is frequently topically used for musculoskeletal pain. Because the commercially available strengths (1 and 2 %) of DS often do not effectively reduce the inflammatory pain, doctors began to prescribe 5%, 10%, 15%, or even higher doses to increase the therapeutic effect¹. However, increasing the dose does not necessarily mean that more drug reaches the target area but instead raise the risk of side effects². Topical microemulsion (ME) is a novel and advanced topical delivery system that can enhance drug solubility and permeability across the skin. Foams have excellent patient compliance due to their ease of administration and the convenience of application. This study investigated a foamable ME as an alternative dosage form to improve the topical delivery of DS.

Methods: The physicochemical properties (optical clarity, percentage transmittance, homogeneity, consistency of formulation, globule size, polydispersity index (PdI), zeta potential, pH, conductivity, viscosity, and morphology) of the microemulsion with and without DS were investigated. The foam quality and foam stability with and without DS were determined over 90 days. Franz diffusion cells were used to assess the in vitro drug release from a DS-loaded foam and compared with a commercial topical product.

Results: A foamable DS-loaded ME was successfully formulated by evaluating the transparency and translucency (refractive index: 1.36 ± 0.00 and transmittance: 98.89 ± 0.67), globule size (22.73 ± 0.15 nm), PdI (0.21 ± 0.01), and zeta potential (-34.40 ± 2.26 mV). It was stable for 90 days (0 day: 21.51± 0.15 nm and 90 days: 20.70 ± 0.56 nm). The foam exhibited an increased rate and extent of drug release (6h: 74.21 ± 9.89 %) compared to the commercial product (6h: 35.51 ± 1.95 %).

Conclusion: The tested foamable ME formulation has great potential to enhance the topical delivery of DS for pain management locally. Foamable ME is a promising alternative to the current topical formulation of DS.

References: 1. Zur E. Topical treatment of neuropathic pain using compounded medications. Clin J Pain. 2014; 30(1): 73–91.
2. Hajjar B., Zier K.I., Khalid N., Azarmi S., Löbenberg R. Evaluation of a microemulsion-based gel formulation for topical drug delivery of diclofenac sodium. J. Pharm. Investig. 2018;48:351–362.

Acknowledgements:

Funding: This study is supported by Taibah University (Saudi Arabia), Alberta Innovates Graduate Student Scholarship (Canada), and Mitacs Accelerate (IT24899, Canada).
Disclosure
*The original study has been published as Hajjar B, Zuo J, Park C, Azarmi S, Silva DA, Bou-Chacra NA, Löbenberg R. In vitro evaluation of a foamable microemulsion towards an improved topical delivery of diclofenac sodium. AAPS PharmSciTech. 2022;23(4):1-9
*This abstract has been accepted for 2022 CSPS annual symposium.